diff --git a/creusot-contracts/src/logic.rs b/creusot-contracts/src/logic.rs
index f923da0be..7da466a3d 100644
--- a/creusot-contracts/src/logic.rs
+++ b/creusot-contracts/src/logic.rs
@@ -5,7 +5,7 @@
 #![cfg_attr(not(creusot), allow(unused_imports))]
 
 mod fmap;
-mod fset;
+pub mod fset;
 mod int;
 mod mapping;
 pub mod ops;
diff --git a/creusot-contracts/src/logic/fset.rs b/creusot-contracts/src/logic/fset.rs
index 469bbb09c..296fa1fb4 100644
--- a/creusot-contracts/src/logic/fset.rs
+++ b/creusot-contracts/src/logic/fset.rs
@@ -1,4 +1,4 @@
-use crate::*;
+use crate::{logic::Mapping, *};
 
 /// A finite set type usable in pearlite and `ghost!` blocks.
 ///
@@ -142,6 +142,15 @@ impl<T: ?Sized> FSet<T> {
         Self::is_subset(other, self)
     }
 
+    /// Returns `true` if `self` and `other` are disjoint.
+    #[trusted]
+    #[predicate]
+    #[creusot::builtins = "set.Fset.disjoint"]
+    pub fn disjoint(self, other: Self) -> bool {
+        let _ = other;
+        dead
+    }
+
     /// Returns the number of elements in the set, also called its length.
     #[trusted]
     #[logic]
@@ -171,8 +180,6 @@ impl<T: ?Sized> FSet<T> {
     /// Returns `true` if `self` and `other` contain exactly the same elements.
     ///
     /// This is in fact equivalent with normal equality.
-    // FIXME: remove `trusted`
-    #[trusted]
     #[open]
     #[predicate]
     #[ensures(result ==> self == other)]
@@ -186,6 +193,119 @@ impl<T: ?Sized> FSet<T> {
     }
 }
 
+impl<T> FSet<T> {
+    /// Returns the set containing only `x`.
+    #[logic]
+    #[open]
+    #[ensures(forall<y: T> result.contains(y) == (x == y))]
+    pub fn singleton(x: T) -> Self {
+        FSet::EMPTY.insert(x)
+    }
+
+    /// Returns the union of sets `f(t)` over all `t: T`.
+    #[logic]
+    #[open]
+    #[ensures(forall<y: U> result.contains(y) == exists<x: T> self.contains(x) && f.get(x).contains(y))]
+    #[variant(self.len())]
+    pub fn unions<U>(self, f: Mapping<T, FSet<U>>) -> FSet<U> {
+        if self.len() == 0 {
+            FSet::EMPTY
+        } else {
+            let x = self.peek();
+            f.get(x).union(self.remove(x).unions(f))
+        }
+    }
+
+    /// Flipped `map`.
+    #[logic]
+    #[trusted]
+    #[creusot::builtins = "set.Fset.map"]
+    pub fn fmap<U>(_: Mapping<T, U>, _: Self) -> FSet<U> {
+        dead
+    }
+
+    /// Returns the image of a set by a function.
+    #[logic]
+    #[open]
+    pub fn map<U>(self, f: Mapping<T, U>) -> FSet<U> {
+        FSet::fmap(f, self)
+    }
+
+    /// Returns the subset of elements of `self` which satisfy the predicate `f`.
+    #[logic]
+    #[trusted]
+    #[creusot::builtins = "set.Fset.filter"]
+    pub fn filter(self, f: Mapping<T, bool>) -> Self {
+        let _ = f;
+        dead
+    }
+
+    /// Returns the set of sequences whose head is in `s` and whose tail is in `ss`.
+    #[logic]
+    #[trusted] // TODO: remove. Needs support for closures in logic functions with constraints
+    #[open]
+    #[ensures(forall<xs: Seq<T>> result.contains(xs) == (0 < xs.len() && s.contains(xs[0]) && ss.contains(xs.tail())))]
+    pub fn cons(s: FSet<T>, ss: FSet<Seq<T>>) -> FSet<Seq<T>> {
+        s.unions(|x| ss.map(|xs: Seq<_>| xs.push_front(x)))
+    }
+
+    /// Returns the set of concatenations of a sequence in `s` and a sequence in `t`.
+    #[logic]
+    #[trusted] // TODO: remove. Needs support for closures in logic functions with constraints
+    #[open]
+    #[ensures(forall<xs: Seq<T>> result.contains(xs) == (exists<ys: Seq<T>, zs: Seq<T>> s.contains(ys) && t.contains(zs) && xs == ys.concat(zs)))]
+    pub fn concat(s: FSet<Seq<T>>, t: FSet<Seq<T>>) -> FSet<Seq<T>> {
+        s.unions(|ys: Seq<_>| t.map(|zs| ys.concat(zs)))
+    }
+
+    /// Returns the set of sequences of length `n` whose elements are in `self`.
+    #[open]
+    #[logic]
+    #[requires(n >= 0)]
+    #[ensures(forall<xs: Seq<T>> result.contains(xs) == (xs.len() == n && forall<x: T> xs.contains(x) ==> self.contains(x)))]
+    #[variant(n)]
+    pub fn replicate(self, n: Int) -> FSet<Seq<T>> {
+        pearlite! {
+            if n == 0 {
+                proof_assert! { forall<xs: Seq<T>> xs.len() == 0 ==> xs == Seq::EMPTY };
+                FSet::singleton(Seq::EMPTY)
+            } else {
+                proof_assert! { forall<xs: Seq<T>, i: Int> 0 < i && i < xs.len() ==> xs[i] == xs.tail()[i-1] };
+                FSet::cons(self, self.replicate(n - 1))
+            }
+        }
+    }
+
+    /// Returns the set of sequences of length at most `n` whose elements are in `self`.
+    #[open]
+    #[logic]
+    #[requires(n >= 0)]
+    #[ensures(forall<xs: Seq<T>> result.contains(xs) == (xs.len() <= n && forall<x: T> xs.contains(x) ==> self.contains(x)))]
+    #[variant(n)]
+    pub fn replicate_up_to(self, n: Int) -> FSet<Seq<T>> {
+        pearlite! {
+            if n == 0 {
+                proof_assert! { forall<xs: Seq<T>> xs.len() == 0 ==> xs == Seq::EMPTY };
+                FSet::singleton(Seq::EMPTY)
+            } else {
+                self.replicate_up_to(n - 1).union(self.replicate(n))
+            }
+        }
+    }
+}
+
+impl FSet<Int> {
+    /// Return the interval of integers in `[i, j)`.
+    #[logic]
+    #[open]
+    #[trusted]
+    #[creusot::builtins = "set.FsetInt.interval"]
+    pub fn interval(i: Int, j: Int) -> FSet<Int> {
+        let _ = (i, j);
+        dead
+    }
+}
+
 /// Ghost definitions
 impl<T: ?Sized> FSet<T> {
     /// Create a new, empty set on the ghost heap.
@@ -337,3 +457,84 @@ impl<T: ?Sized> Invariant for FSet<T> {
         pearlite! { forall<x: &T> self.contains(*x) ==> inv(*x) }
     }
 }
+
+// Properties
+
+/// Distributivity of `unions` over `union`.
+#[logic]
+#[open]
+#[ensures(forall<s1: FSet<T>, s2: FSet<T>, f: Mapping<T, FSet<U>>> s1.union(s2).unions(f) == s1.unions(f).union(s2.unions(f)))]
+#[ensures(forall<s: FSet<T>, f: Mapping<T, FSet<U>>, g: Mapping<T, FSet<U>>>
+    s.unions(|x| f.get(x).union(g.get(x))) == s.unions(f).union(s.unions(g)))]
+pub fn unions_union<T, U>() {}
+
+/// Distributivity of `map` over `union`.
+#[logic]
+#[open]
+#[ensures(forall<s: FSet<T>, t: FSet<T>, f: Mapping<T, U>> s.union(t).map(f) == s.map(f).union(t.map(f)))]
+pub fn map_union<T, U>() {}
+
+/// Distributivity of `concat` over `union`.
+#[logic]
+#[open]
+#[ensures(forall<s1: FSet<Seq<T>>, s2: FSet<Seq<T>>, t: FSet<Seq<T>>>
+    FSet::concat(s1.union(s2), t) == FSet::concat(s1, t).union(FSet::concat(s2, t)))]
+#[ensures(forall<s: FSet<Seq<T>>, t1: FSet<Seq<T>>, t2: FSet<Seq<T>>>
+    FSet::concat(s, t1.union(t2)) == FSet::concat(s, t1).union(FSet::concat(s, t2)))]
+pub fn concat_union<T>() {}
+
+/// Distributivity of `cons` over `union`.
+#[logic]
+#[open]
+#[ensures(forall<s: FSet<T>, t: FSet<Seq<T>>, u: FSet<Seq<T>>> FSet::concat(FSet::cons(s, t), u) == FSet::cons(s, FSet::concat(t, u)))]
+pub fn cons_concat<T>() {
+    proof_assert! { forall<x: T, xs: Seq<T>, ys: Seq<T>> xs.push_front(x).concat(ys) == xs.concat(ys).push_front(x) };
+    proof_assert! { forall<x: T, ys: Seq<T>> ys.push_front(x).tail() == ys };
+    proof_assert! { forall<ys: Seq<T>> 0 < ys.len() ==> ys == ys.tail().push_front(ys[0]) };
+}
+
+/// Distributivity of `replicate` over `union`.
+#[logic]
+#[open]
+#[requires(0 <= n && 0 <= m)]
+#[ensures(s.replicate(n + m) == FSet::concat(s.replicate(n), s.replicate(m)))]
+#[variant(n)]
+pub fn concat_replicate<T>(n: Int, m: Int, s: FSet<T>) {
+    pearlite! {
+        if n == 0 {
+            concat_empty(s.replicate(m));
+        } else {
+            cons_concat::<T>();
+            concat_replicate(n - 1, m, s);
+        }
+    }
+}
+
+/// The neutral element of `FSet::concat` is `FSet::singleton(Seq::EMPTY)`.
+#[logic]
+#[open]
+#[ensures(FSet::concat(FSet::singleton(Seq::EMPTY), s) == s)]
+#[ensures(FSet::concat(s, FSet::singleton(Seq::EMPTY)) == s)]
+pub fn concat_empty<T>(s: FSet<Seq<T>>) {
+    proof_assert! { forall<xs: Seq<T>> xs.concat(Seq::EMPTY) == xs };
+    proof_assert! { forall<xs: Seq<T>> Seq::EMPTY.concat(xs) == xs };
+}
+
+/// An equation relating `s.replicate_up_to(m)` and `s.replicate_up_to(n)`.
+#[logic]
+#[open]
+#[requires(0 <= n && n < m)]
+#[ensures(s.replicate_up_to(m) == s.replicate_up_to(n).union(
+    FSet::concat(s.replicate(n + 1), s.replicate_up_to(m - n - 1))))]
+#[variant(m)]
+pub fn concat_replicate_up_to<T>(n: Int, m: Int, s: FSet<T>) {
+    pearlite! {
+        if n + 1 == m {
+            concat_empty(s.replicate(n + 1));
+        } else {
+            concat_union::<T>();
+            concat_replicate(n, m - n - 1, s);
+            concat_replicate_up_to(n, m - 1, s);
+        }
+    }
+}
diff --git a/creusot-contracts/src/std.rs b/creusot-contracts/src/std.rs
index 08c594887..ddfc347ff 100644
--- a/creusot-contracts/src/std.rs
+++ b/creusot-contracts/src/std.rs
@@ -1,6 +1,7 @@
 pub use ::std::*;
 
 pub mod array;
+pub mod borrow;
 pub mod boxed;
 pub mod clone;
 pub mod collections {
diff --git a/creusot-contracts/src/std/borrow.rs b/creusot-contracts/src/std/borrow.rs
new file mode 100644
index 000000000..d2fdd19f0
--- /dev/null
+++ b/creusot-contracts/src/std/borrow.rs
@@ -0,0 +1,18 @@
+use crate::*;
+use ::std::borrow::Borrow;
+
+extern_spec! {
+    mod std {
+        mod borrow {
+            trait Borrow<Borrowed>
+            where Borrowed: ?Sized
+            {
+                #[ensures(result.deep_model() == self.deep_model())]
+                fn borrow(&self) -> &Borrowed
+                where
+                    Self: DeepModel,
+                    Borrowed: DeepModel<DeepModelTy = Self::DeepModelTy>;
+            }
+        }
+    }
+}
diff --git a/creusot-contracts/src/std/collections/hash_set.rs b/creusot-contracts/src/std/collections/hash_set.rs
index 41bd35d58..a5b16c7b0 100644
--- a/creusot-contracts/src/std/collections/hash_set.rs
+++ b/creusot-contracts/src/std/collections/hash_set.rs
@@ -3,7 +3,7 @@ use crate::{
     std::iter::{FromIterator, IntoIterator, Iterator},
     *,
 };
-use ::std::{collections::hash_set::*, hash::*};
+use ::std::{borrow::Borrow, collections::hash_set::*, hash::*};
 
 impl<T: DeepModel, S> View for HashSet<T, S> {
     type ViewTy = FSet<T::DeepModelTy>;
@@ -31,6 +31,12 @@ extern_spec! {
                 {
                     #[ensures(result@ == self@.intersection(other@))]
                     fn intersection<'a>(&'a self, other: &'a HashSet<T,S>) -> Intersection<'a, T, S>;
+
+                    #[ensures(result == self@.contains(value.deep_model()))]
+                    fn contains<Q: ?Sized>(&self, value: &Q) -> bool
+                    where
+                        T: Borrow<Q>,
+                        Q: Eq + Hash + DeepModel<DeepModelTy = T::DeepModelTy>;
                 }
             }
         }
diff --git a/creusot-contracts/src/std/iter.rs b/creusot-contracts/src/std/iter.rs
index be4286824..83ffcfe39 100644
--- a/creusot-contracts/src/std/iter.rs
+++ b/creusot-contracts/src/std/iter.rs
@@ -6,12 +6,14 @@ mod copied;
 mod empty;
 mod enumerate;
 mod filter;
+mod filter_map;
 mod fuse;
 mod map;
 mod map_inv;
 mod once;
 mod range;
 mod repeat;
+mod rev;
 mod skip;
 mod take;
 mod zip;
@@ -20,9 +22,11 @@ pub use cloned::ClonedExt;
 pub use copied::CopiedExt;
 pub use enumerate::EnumerateExt;
 pub use filter::FilterExt;
+pub use filter_map::FilterMapExt;
 pub use fuse::FusedIterator;
 pub use map::MapExt;
 pub use map_inv::MapInv;
+pub use rev::RevExt;
 pub use skip::SkipExt;
 pub use take::TakeExt;
 pub use zip::ZipExt;
@@ -94,6 +98,37 @@ pub trait FromIterator<A>: ::std::iter::FromIterator<A> {
     fn from_iter_post(prod: Seq<A>, res: Self) -> bool;
 }
 
+pub trait DoubleEndedIterator: ::std::iter::DoubleEndedIterator + Iterator {
+    #[predicate(prophetic)]
+    fn produces_back(self, visited: Seq<Self::Item>, o: Self) -> bool;
+
+    #[law]
+    #[ensures(self.produces_back(Seq::EMPTY, self))]
+    fn produces_back_refl(self);
+
+    #[law]
+    #[requires(a.produces_back(ab, b))]
+    #[requires(b.produces_back(bc, c))]
+    #[ensures(a.produces_back(ab.concat(bc), c))]
+    fn produces_back_trans(a: Self, ab: Seq<Self::Item>, b: Self, bc: Seq<Self::Item>, c: Self);
+
+    // FIXME: remove `trusted`
+    #[trusted]
+    #[requires(forall<e : Self::Item, i2 : Self>
+                    self.produces_back(Seq::singleton(e), i2) ==>
+                    func.precondition((e, Snapshot::new(Seq::EMPTY))))]
+    #[requires(MapInv::<Self, _, F>::reinitialize())]
+    #[requires(MapInv::<Self, Self::Item, F>::preservation(self, func))]
+    #[ensures(result == MapInv { iter: self, func, produced: Snapshot::new(Seq::EMPTY) })]
+    fn map_inv_back<B, F>(self, func: F) -> MapInv<Self, Self::Item, F>
+    where
+        Self: Sized,
+        F: FnMut(Self::Item, Snapshot<Seq<Self::Item>>) -> B,
+    {
+        MapInv { iter: self, func, produced: snapshot! {Seq::EMPTY} }
+    }
+}
+
 extern_spec! {
     mod std {
         mod iter {
@@ -144,6 +179,13 @@ extern_spec! {
                 fn filter<P>(self, f: P) -> Filter<Self, P>
                     where  P : for<'a> FnMut(&Self_::Item) -> bool;
 
+                #[pure]
+                #[requires(filter_map::immutable(f))]
+                #[requires(filter_map::no_precondition(f))]
+                #[requires(filter_map::precise(f))]
+                #[ensures(result.iter() == self && result.func() == f)]
+                fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>
+                    where F : for<'a> FnMut(Self_::Item) -> Option<B>;
 
                 #[pure]
                 // These two requirements are here only to prove the absence of overflows
@@ -167,6 +209,11 @@ extern_spec! {
                     resolve(&^done) && done.completed() && self.produces(prod, *done) && B::from_iter_post(prod, result))]
                 fn collect<B>(self) -> B
                     where B: FromIterator<Self::Item>;
+
+                #[pure]
+                #[ensures(result.iter() == self)]
+                fn rev(self) -> Rev<Self>
+                    where Self: Sized + DoubleEndedIterator;
             }
 
             trait IntoIterator
@@ -200,6 +247,15 @@ extern_spec! {
             #[pure]
             #[ensures(result@ == elt)]
             fn repeat<T: Clone>(elt: T) -> Repeat<T>;
+
+            trait DoubleEndedIterator
+                where Self: DoubleEndedIterator {
+                #[ensures(match result {
+                    None => self.completed(),
+                    Some(v) => (*self).produces_back(Seq::singleton(v), ^self)
+                })]
+                fn next_back(&mut self) -> Option<Self::Item>;
+            }
         }
     }
 }
diff --git a/creusot-contracts/src/std/iter/filter.rs b/creusot-contracts/src/std/iter/filter.rs
index ebc8b229b..f4a560775 100644
--- a/creusot-contracts/src/std/iter/filter.rs
+++ b/creusot-contracts/src/std/iter/filter.rs
@@ -90,13 +90,12 @@ where
             // Interestingly, Z3 guesses `f` quite readily but gives up *totally* on `s`. However, the addition of the final assertions on the correctness of the values
             // blocks z3's guess for `f`.
             exists<s : Seq<Self::Item>, f : Mapping<Int, Int>> self.iter().produces(s, succ.iter()) &&
+                (forall<i: Int> 0 <= i && i < visited.len() ==> 0 <= f.get(i) && f.get(i) < s.len()) &&
                 // `f` is a monotone mapping
-                (forall<i : _, j :_ > 0 <= i && i <= j && j < visited.len() ==> 0 <= f.get(i) && f.get(i) <= f.get(j) && f.get(j) < s.len()) &&
+                (forall<i: _, j:_ > 0 <= i && i < j && j < visited.len() ==> f.get(i) < f.get(j)) &&
                 (forall<i : _, > 0 <= i && i < visited.len() ==> visited[i] == s[f.get(i)]) &&
-
                 (forall<i : _> 0 <= i &&  i < s.len() ==>
-                    (exists<j : _> 0 <= j && j < visited.len() && f.get(j) == i) == self.func().postcondition_mut((&s[i],), self.func(), true)
-                )
+                    (exists<j : _> 0 <= j && j < visited.len() && f.get(j) == i) == self.func().postcondition_mut((&s[i],), self.func(), true))
         }
     }
 
diff --git a/creusot-contracts/src/std/iter/filter_map.rs b/creusot-contracts/src/std/iter/filter_map.rs
new file mode 100644
index 000000000..06d533af4
--- /dev/null
+++ b/creusot-contracts/src/std/iter/filter_map.rs
@@ -0,0 +1,113 @@
+use crate::{logic::Mapping, std::ops::*, *};
+use ::std::iter::FilterMap;
+
+pub trait FilterMapExt<I, F> {
+    #[logic]
+    fn iter(self) -> I;
+
+    #[logic]
+    fn func(self) -> F;
+}
+
+impl<I, F> FilterMapExt<I, F> for FilterMap<I, F> {
+    #[trusted]
+    #[logic]
+    #[ensures(inv(self) ==> inv(result))]
+    fn iter(self) -> I {
+        dead
+    }
+
+    #[trusted]
+    #[logic]
+    #[ensures(inv(self) ==> inv(result))]
+    fn func(self) -> F {
+        dead
+    }
+}
+
+impl<B, I: Iterator, F: FnMut(I::Item) -> Option<B>> Invariant for FilterMap<I, F> {
+    #[predicate(prophetic)]
+    #[open(self)]
+    fn invariant(self) -> bool {
+        pearlite! {
+            // trivial precondition: simplification for sake of proof complexity
+            no_precondition(self.func()) &&
+            // immutable state: simplification for sake of proof complexity
+            immutable(self.func()) &&
+            // precision of postcondition
+            precise(self.func())
+        }
+    }
+}
+
+/// Asserts that `f` has no precondition: any closure state can be called with any input value
+/// In a future release this restriction may be lifted or weakened
+#[open]
+#[predicate(prophetic)]
+pub fn no_precondition<A, B, F: FnMut(A) -> Option<B>>(f: F) -> bool {
+    pearlite! { forall<i : A> f.precondition((i,)) }
+}
+
+/// Asserts that the captures of `f` are used immutably
+/// In a future release this restriction may be lifted or weakened
+#[open]
+#[predicate(prophetic)]
+pub fn immutable<A, B, F: FnMut(A) -> Option<B>>(f: F) -> bool {
+    pearlite! { forall<g : F> f.unnest(g) ==> f == g }
+}
+
+/// Asserts that the postcondition of `f` is *precise*: that there are never two possible values matching the postcondition
+#[open]
+#[predicate(prophetic)]
+pub fn precise<A, B, F: FnMut(A) -> Option<B>>(f1: F) -> bool {
+    pearlite! { forall<f2 : F, i : _> !((exists<b: B> f1.postcondition_mut((i,), f2, Some(b))) && f1.postcondition_mut((i,), f2, None)) }
+}
+
+impl<I, B, F> Iterator for FilterMap<I, F>
+where
+    I: Iterator,
+    F: FnMut(I::Item) -> Option<B>,
+{
+    #[open]
+    #[predicate(prophetic)]
+    fn completed(&mut self) -> bool {
+        pearlite! {
+            (exists<s: Seq<_>, e : &mut I > self.iter().produces(s, *e) && e.completed() &&
+                forall<i : _> 0 <= i && i < s.len() ==> (*self).func().postcondition_mut((s[i],), (^self).func(), None))
+            && (*self).func() == (^self).func()
+        }
+    }
+
+    #[open]
+    #[predicate(prophetic)]
+    fn produces(self, visited: Seq<Self::Item>, succ: Self) -> bool {
+        pearlite! {
+            self.invariant() ==>
+            self.func().unnest(succ.func()) &&
+            // f here is a mapping from indices of `visited` to those of `s`, where `s` is the whole sequence produced by the underlying iterator
+            // Interestingly, Z3 guesses `f` quite readily but gives up *totally* on `s`. However, the addition of the final assertions on the correctness of the values
+            // blocks z3's guess for `f`.
+            exists<s : Seq<I::Item>, f : Mapping<Int, Int>> self.iter().produces(s, succ.iter()) &&
+                (forall<i: Int> 0 <= i && i < visited.len() ==> 0 <= f.get(i) && f.get(i) < s.len()) &&
+                // `f` is a monotone mapping
+                (forall<i: _, j:_ > 0 <= i && i < j && j < visited.len() ==> f.get(i) < f.get(j)) &&
+                // `f` points to elements produced in `s` (by the underlying `iter`) for which the predicate `self.func()` returned `Some`.
+                (forall<i: Int> 0 <= i && i < visited.len() ==> self.func().postcondition_mut((s[f.get(i)],), self.func(), Some(visited[i]))) &&
+                // For other elements not in the image of `f`, the predicate `self.func()` returned `None`.
+                (forall<j: Int> 0 <= j && j < s.len()
+                    ==> (!exists<i: Int> 0 <= i && i < visited.len() && f.get(i) == j) == self.func().postcondition_mut((s[j],), self.func(), None))
+        }
+    }
+
+    #[law]
+    #[open(self)]
+    #[ensures(self.produces(Seq::EMPTY, self))]
+    fn produces_refl(self) {}
+
+    #[law]
+    #[open(self)]
+    #[requires(a.produces(ab, b))]
+    #[requires(b.produces(bc, c))]
+    #[ensures(a.produces(ab.concat(bc), c))]
+    fn produces_trans(a: Self, ab: Seq<Self::Item>, b: Self, bc: Seq<Self::Item>, c: Self) {}
+}
diff --git a/creusot-contracts/src/std/iter/range.rs b/creusot-contracts/src/std/iter/range.rs
index 2a21d42f9..2fa602912 100644
--- a/creusot-contracts/src/std/iter/range.rs
+++ b/creusot-contracts/src/std/iter/range.rs
@@ -1,6 +1,6 @@
 use crate::{
     std::{
-        iter::Step,
+        iter::{DoubleEndedIterator, Step},
         ops::{Range, RangeInclusive},
     },
     *,
@@ -40,6 +40,32 @@ impl<Idx: DeepModel<DeepModelTy = Int> + Step> Iterator for Range<Idx> {
     fn produces_trans(a: Self, ab: Seq<Self::Item>, b: Self, bc: Seq<Self::Item>, c: Self) {}
 }
 
+impl<Idx: DeepModel<DeepModelTy = Int> + Step> DoubleEndedIterator for Range<Idx> {
+    #[predicate]
+    #[open]
+    fn produces_back(self, visited: Seq<Self::Item>, o: Self) -> bool {
+        pearlite! {
+            self.start == o.start && self.end.deep_model() >= o.end.deep_model()
+            && (visited.len() > 0 ==> o.end.deep_model() >= o.start.deep_model())
+            && visited.len() == o.end.deep_model() - self.end.deep_model()
+            && forall<i : Int> 0 <= i && i < visited.len() ==>
+                visited[i].deep_model() == self.end.deep_model() - i
+        }
+    }
+
+    #[law]
+    #[open(self)]
+    #[ensures(self.produces_back(Seq::EMPTY, self))]
+    fn produces_back_refl(self) {}
+
+    #[law]
+    #[open(self)]
+    #[requires(a.produces_back(ab, b))]
+    #[requires(b.produces_back(bc, c))]
+    #[ensures(a.produces_back(ab.concat(bc), c))]
+    fn produces_back_trans(a: Self, ab: Seq<Self::Item>, b: Self, bc: Seq<Self::Item>, c: Self) {}
+}
+
 #[logic]
 #[open]
 #[ensures(r.is_empty_log() == (result == 0))]
@@ -83,3 +109,29 @@ impl<Idx: DeepModel<DeepModelTy = Int> + Step> Iterator for RangeInclusive<Idx>
     #[ensures(a.produces(ab.concat(bc), c))]
     fn produces_trans(a: Self, ab: Seq<Self::Item>, b: Self, bc: Seq<Self::Item>, c: Self) {}
 }
+
+impl<Idx: DeepModel<DeepModelTy = Int> + Step> DoubleEndedIterator for RangeInclusive<Idx> {
+    #[predicate]
+    #[open]
+    fn produces_back(self, visited: Seq<Self::Item>, o: Self) -> bool {
+        pearlite! {
+            visited.len() == range_inclusive_len(self) - range_inclusive_len(o) &&
+            (self.is_empty_log() ==> o.is_empty_log()) &&
+            (o.is_empty_log() || self.start_log() == o.start_log()) &&
+            forall<i : Int> 0 <= i && i < visited.len() ==>
+                visited[i].deep_model() == self.end_log().deep_model() - i
+        }
+    }
+
+    #[law]
+    #[open]
+    #[ensures(self.produces_back(Seq::EMPTY, self))]
+    fn produces_back_refl(self) {}
+
+    #[law]
+    #[open]
+    #[requires(a.produces_back(ab, b))]
+    #[requires(b.produces_back(bc, c))]
+    #[ensures(a.produces_back(ab.concat(bc), c))]
+    fn produces_back_trans(a: Self, ab: Seq<Self::Item>, b: Self, bc: Seq<Self::Item>, c: Self) {}
+}
diff --git a/creusot-contracts/src/std/iter/rev.rs b/creusot-contracts/src/std/iter/rev.rs
new file mode 100644
index 000000000..c771a4343
--- /dev/null
+++ b/creusot-contracts/src/std/iter/rev.rs
@@ -0,0 +1,56 @@
+use crate::{
+    std::iter::{DoubleEndedIterator, Iterator, Rev},
+    *,
+};
+
+pub trait RevExt<I> {
+    #[logic]
+    fn iter(self) -> I;
+
+    #[logic]
+    fn iter_mut(&mut self) -> &mut I;
+}
+
+impl<I> RevExt<I> for Rev<I> {
+    #[logic]
+    #[trusted]
+    #[ensures(inv(self) ==> inv(result))]
+    fn iter(self) -> I {
+        dead
+    }
+
+    #[logic]
+    #[trusted]
+    #[ensures((*self).iter() == *result && (^self).iter() == ^result)]
+    fn iter_mut(&mut self) -> &mut I {
+        dead
+    }
+}
+
+impl<I: DoubleEndedIterator> Iterator for Rev<I> {
+    #[open]
+    #[predicate(prophetic)]
+    fn completed(&mut self) -> bool {
+        pearlite! { self.iter_mut().completed() }
+    }
+
+    #[open]
+    #[predicate(prophetic)]
+    fn produces(self, visited: Seq<Self::Item>, o: Self) -> bool {
+        pearlite! {
+            self.iter().produces_back(visited, o.iter())
+        }
+    }
+
+    #[law]
+    #[open(self)]
+    #[ensures(self.produces(Seq::EMPTY, self))]
+    fn produces_refl(self) {}
+
+    #[law]
+    #[open(self)]
+    #[requires(a.produces(ab, b))]
+    #[requires(b.produces(bc, c))]
+    #[ensures(a.produces(ab.concat(bc), c))]
+    fn produces_trans(a: Self, ab: Seq<Self::Item>, b: Self, bc: Seq<Self::Item>, c: Self) {}
+}
diff --git a/creusot/tests/creusot-contracts/creusot-contracts.coma b/creusot/tests/creusot-contracts/creusot-contracts.coma
index 7b8d0eaf4..3d03a6d53 100644
--- a/creusot/tests/creusot-contracts/creusot-contracts.coma
+++ b/creusot/tests/creusot-contracts/creusot-contracts.coma
@@ -1111,15 +1111,15 @@ module M_creusot_contracts__stdqy35z1__collections__hash_map__qyi160525698381677
    -> Seq.get bc i = Seq.get (Seq.(++) ab bc) (Seq.length ab + i))
   && (let _ = () in [%#shash_map2] produces'0 a (Seq.(++) ab bc) c)
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__set_produces_trans [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 74 0 80 1]
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 71 11 71 33
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 72 11 72 33
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 73 10 73 43
+module M_creusot_contracts__stdqy35z1__collections__hash_set__set_produces_trans [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 80 0 86 1]
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 77 11 77 33
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 78 11 78 33
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 79 10 79 43
   let%span sseq3 = "../../../creusot-contracts/src/logic/seq.rs" 382 14 383 65
-  let%span shash_set4 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 82 20 82 108
-  let%span shash_set5 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 83 20 83 98
-  let%span shash_set6 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 81 4 81 31
-  let%span shash_set7 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+  let%span shash_set4 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 88 20 88 108
+  let%span shash_set5 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 89 20 89 98
+  let%span shash_set6 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 87 4 87 31
+  let%span shash_set7 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sseq8 = "../../../creusot-contracts/src/logic/seq.rs" 381 4 381 12
   let%span sseq9 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
   let%span sseq10 = "../../../creusot-contracts/src/logic/seq.rs" 80 4 80 12
@@ -1158,7 +1158,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__set_produces_trans
    =
     [%#sseq9] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_I'0) (visited : Seq.seq t_T'0) (end' : t_I'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_I'0) (visited : Seq.seq t_T'0) (end' : t_I'0)
     
    =
     [%#shash_set7] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -1201,7 +1201,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__set_produces_trans
   
   constant c  : t_I'0
   
-  function set_produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 74 0 80 1] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
+  function set_produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 80 0 86 1] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
     
   
   goal vc_set_produces_trans'0 : ([%#shash_set1] set_produces'0 b bc c)
@@ -1214,11 +1214,11 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__set_produces_trans
    -> Seq.get bc i = Seq.get (Seq.(++) ab bc) (Seq.length ab + i))
   && (let _ = () in let _ = () in [%#shash_set2] set_produces'0 a (Seq.(++) ab bc) c)))
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi2602027177218488890__produces_refl [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 102 4 102 26] (* <std::collections::hash_set::IntoIter<T> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 101 14 101 45
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 99 4 99 10
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 90 8 90 38
-  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi2602027177218488890__produces_refl [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 108 4 108 26] (* <std::collections::hash_set::IntoIter<T> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 107 14 107 45
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 105 4 105 10
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 96 8 96 38
+  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span sseq5 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
   
@@ -1350,7 +1350,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 46 4 46 33] (self : t_IntoIter'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 52 4 52 33] (self : t_IntoIter'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -1374,7 +1374,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
    =
     [%#sseq5] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_IntoIter'0) (visited : Seq.seq t_T'0) (end' : t_IntoIter'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_IntoIter'0) (visited : Seq.seq t_T'0) (end' : t_IntoIter'0)
     
    =
     [%#shash_set3] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -1389,29 +1389,29 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 89 4 89 64] (self : t_IntoIter'0) (visited : Seq.seq t_T'0) (o : t_IntoIter'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 95 4 95 64] (self : t_IntoIter'0) (visited : Seq.seq t_T'0) (o : t_IntoIter'0)
     
    =
     [%#shash_set2] set_produces'0 self visited o
   
   constant self  : t_IntoIter'0
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 102 4 102 26] (self : t_IntoIter'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 108 4 108 26] (self : t_IntoIter'0) : ()
     
   
   goal vc_produces_refl'0 : [%#shash_set0] produces'0 self (Seq.empty  : Seq.seq t_T'0) self
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi2602027177218488890__produces_trans [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 109 4 109 90] (* <std::collections::hash_set::IntoIter<T> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 106 15 106 32
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 107 15 107 32
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 108 14 108 42
-  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 71 11 71 33
-  let%span shash_set4 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 72 11 72 33
-  let%span shash_set5 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 73 10 73 43
-  let%span shash_set6 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 110 8 110 43
-  let%span shash_set7 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 90 8 90 38
-  let%span shash_set8 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 81 4 81 31
-  let%span shash_set9 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi2602027177218488890__produces_trans [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 115 4 115 90] (* <std::collections::hash_set::IntoIter<T> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 112 15 112 32
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 113 15 113 32
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 114 14 114 42
+  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 77 11 77 33
+  let%span shash_set4 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 78 11 78 33
+  let%span shash_set5 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 79 10 79 43
+  let%span shash_set6 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 116 8 116 43
+  let%span shash_set7 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 96 8 96 38
+  let%span shash_set8 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 87 4 87 31
+  let%span shash_set9 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sseq10 = "../../../creusot-contracts/src/logic/seq.rs" 382 14 383 65
   let%span sseq11 = "../../../creusot-contracts/src/logic/seq.rs" 381 4 381 12
   let%span sfset12 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
@@ -1543,7 +1543,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 46 4 46 33] (self : t_IntoIter'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 52 4 52 33] (self : t_IntoIter'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -1567,7 +1567,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
    =
     [%#sseq13] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_IntoIter'0) (visited : Seq.seq t_T'0) (end' : t_IntoIter'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_IntoIter'0) (visited : Seq.seq t_T'0) (end' : t_IntoIter'0)
     
    =
     [%#shash_set9] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -1582,7 +1582,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 89 4 89 64] (self : t_IntoIter'0) (visited : Seq.seq t_T'0) (o : t_IntoIter'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 95 4 95 64] (self : t_IntoIter'0) (visited : Seq.seq t_T'0) (o : t_IntoIter'0)
     
    =
     [%#shash_set7] set_produces'0 self visited o
@@ -1596,7 +1596,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
   = contains'1 a x
   \/ contains'1 b x
   
-  function set_produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 74 0 80 1] (a : t_IntoIter'0) (ab : Seq.seq t_T'0) (b : t_IntoIter'0) (bc : Seq.seq t_T'0) (c : t_IntoIter'0) : ()
+  function set_produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 80 0 86 1] (a : t_IntoIter'0) (ab : Seq.seq t_T'0) (b : t_IntoIter'0) (bc : Seq.seq t_T'0) (c : t_IntoIter'0) : ()
     
    =
     [%#shash_set8] let _ = concat_contains'0 () in let _ = let _ = () in () in let _ = let _ = () in () in ()
@@ -1614,7 +1614,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
   
   constant c  : t_IntoIter'0
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 109 4 109 90] (a : t_IntoIter'0) (ab : Seq.seq t_T'0) (b : t_IntoIter'0) (bc : Seq.seq t_T'0) (c : t_IntoIter'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 115 4 115 90] (a : t_IntoIter'0) (ab : Seq.seq t_T'0) (b : t_IntoIter'0) (bc : Seq.seq t_T'0) (c : t_IntoIter'0) : ()
     
   
   goal vc_produces_trans'0 : ([%#shash_set1] produces'0 b bc c)
@@ -1624,11 +1624,11 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
   /\ (([%#shash_set5] set_produces'0 a (Seq.(++) ab bc) c)
    -> (let _ = set_produces_trans'0 a ab b bc c in [%#shash_set2] produces'0 a (Seq.(++) ab bc) c))
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi7331660899108484271__produces_refl [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 141 4 141 26] (* <std::collections::hash_set::Iter<'a, T> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 140 14 140 45
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 138 4 138 10
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 129 8 129 38
-  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi7331660899108484271__produces_refl [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 147 4 147 26] (* <std::collections::hash_set::Iter<'a, T> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 146 14 146 45
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 144 4 144 10
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 135 8 135 38
+  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span smodel5 = "../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span sseq6 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
@@ -1684,7 +1684,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 120 4 120 33] (self : t_Iter'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 126 4 126 33] (self : t_Iter'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -1711,7 +1711,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
    =
     [%#sseq6] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_Iter'0) (visited : Seq.seq t_T'0) (end' : t_Iter'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_Iter'0) (visited : Seq.seq t_T'0) (end' : t_Iter'0)
     
    =
     [%#shash_set3] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -1726,29 +1726,29 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 128 4 128 64] (self : t_Iter'0) (visited : Seq.seq t_T'0) (o : t_Iter'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 134 4 134 64] (self : t_Iter'0) (visited : Seq.seq t_T'0) (o : t_Iter'0)
     
    =
     [%#shash_set2] set_produces'0 self visited o
   
   constant self  : t_Iter'0
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 141 4 141 26] (self : t_Iter'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 147 4 147 26] (self : t_Iter'0) : ()
     
   
   goal vc_produces_refl'0 : [%#shash_set0] produces'0 self (Seq.empty  : Seq.seq t_T'0) self
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi7331660899108484271__produces_trans [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 148 4 148 90] (* <std::collections::hash_set::Iter<'a, T> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 145 15 145 32
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 146 15 146 32
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 147 14 147 42
-  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 71 11 71 33
-  let%span shash_set4 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 72 11 72 33
-  let%span shash_set5 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 73 10 73 43
-  let%span shash_set6 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 149 8 149 43
-  let%span shash_set7 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 129 8 129 38
-  let%span shash_set8 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 81 4 81 31
-  let%span shash_set9 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi7331660899108484271__produces_trans [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 154 4 154 90] (* <std::collections::hash_set::Iter<'a, T> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 151 15 151 32
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 152 15 152 32
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 153 14 153 42
+  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 77 11 77 33
+  let%span shash_set4 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 78 11 78 33
+  let%span shash_set5 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 79 10 79 43
+  let%span shash_set6 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 155 8 155 43
+  let%span shash_set7 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 135 8 135 38
+  let%span shash_set8 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 87 4 87 31
+  let%span shash_set9 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sseq10 = "../../../creusot-contracts/src/logic/seq.rs" 382 14 383 65
   let%span sseq11 = "../../../creusot-contracts/src/logic/seq.rs" 381 4 381 12
   let%span sfset12 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
@@ -1804,7 +1804,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 120 4 120 33] (self : t_Iter'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 126 4 126 33] (self : t_Iter'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -1831,7 +1831,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
    =
     [%#sseq14] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_Iter'0) (visited : Seq.seq t_T'0) (end' : t_Iter'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_Iter'0) (visited : Seq.seq t_T'0) (end' : t_Iter'0)
     
    =
     [%#shash_set9] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -1846,7 +1846,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 128 4 128 64] (self : t_Iter'0) (visited : Seq.seq t_T'0) (o : t_Iter'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 134 4 134 64] (self : t_Iter'0) (visited : Seq.seq t_T'0) (o : t_Iter'0)
     
    =
     [%#shash_set7] set_produces'0 self visited o
@@ -1860,7 +1860,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
   = contains'1 a x
   \/ contains'1 b x
   
-  function set_produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 74 0 80 1] (a : t_Iter'0) (ab : Seq.seq t_T'0) (b : t_Iter'0) (bc : Seq.seq t_T'0) (c : t_Iter'0) : ()
+  function set_produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 80 0 86 1] (a : t_Iter'0) (ab : Seq.seq t_T'0) (b : t_Iter'0) (bc : Seq.seq t_T'0) (c : t_Iter'0) : ()
     
    =
     [%#shash_set8] let _ = concat_contains'0 () in let _ = let _ = () in () in let _ = let _ = () in () in ()
@@ -1878,7 +1878,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
   
   constant c  : t_Iter'0
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 148 4 148 90] (a : t_Iter'0) (ab : Seq.seq t_T'0) (b : t_Iter'0) (bc : Seq.seq t_T'0) (c : t_Iter'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 154 4 154 90] (a : t_Iter'0) (ab : Seq.seq t_T'0) (b : t_Iter'0) (bc : Seq.seq t_T'0) (c : t_Iter'0) : ()
     
   
   goal vc_produces_trans'0 : ([%#shash_set1] produces'0 b bc c)
@@ -1888,11 +1888,11 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
   /\ (([%#shash_set5] set_produces'0 a (Seq.(++) ab bc) c)
    -> (let _ = set_produces_trans'0 a ab b bc c in [%#shash_set2] produces'0 a (Seq.(++) ab bc) c))
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi3673804955138978513__produces_refl [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 216 4 216 26] (* <std::collections::hash_set::Intersection<'a, T, S> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 215 14 215 45
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 213 4 213 10
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 204 8 204 38
-  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi3673804955138978513__produces_refl [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 222 4 222 26] (* <std::collections::hash_set::Intersection<'a, T, S> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 221 14 221 45
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 219 4 219 10
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 210 8 210 38
+  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span smodel5 = "../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span sseq6 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
@@ -1974,7 +1974,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 195 4 195 33] (self : t_Intersection'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 201 4 201 33] (self : t_Intersection'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -2001,7 +2001,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
    =
     [%#sseq6] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_Intersection'0) (visited : Seq.seq t_T'0) (end' : t_Intersection'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_Intersection'0) (visited : Seq.seq t_T'0) (end' : t_Intersection'0)
     
    =
     [%#shash_set3] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -2016,29 +2016,29 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 203 4 203 64] (self : t_Intersection'0) (visited : Seq.seq t_T'0) (o : t_Intersection'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 209 4 209 64] (self : t_Intersection'0) (visited : Seq.seq t_T'0) (o : t_Intersection'0)
     
    =
     [%#shash_set2] set_produces'0 self visited o
   
   constant self  : t_Intersection'0
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 216 4 216 26] (self : t_Intersection'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 222 4 222 26] (self : t_Intersection'0) : ()
     
   
   goal vc_produces_refl'0 : [%#shash_set0] produces'0 self (Seq.empty  : Seq.seq t_T'0) self
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi3673804955138978513__produces_trans [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 223 4 223 90] (* <std::collections::hash_set::Intersection<'a, T, S> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 220 15 220 32
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 221 15 221 32
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 222 14 222 42
-  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 71 11 71 33
-  let%span shash_set4 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 72 11 72 33
-  let%span shash_set5 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 73 10 73 43
-  let%span shash_set6 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 224 8 224 43
-  let%span shash_set7 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 204 8 204 38
-  let%span shash_set8 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 81 4 81 31
-  let%span shash_set9 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi3673804955138978513__produces_trans [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 229 4 229 90] (* <std::collections::hash_set::Intersection<'a, T, S> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 226 15 226 32
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 227 15 227 32
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 228 14 228 42
+  let%span shash_set3 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 77 11 77 33
+  let%span shash_set4 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 78 11 78 33
+  let%span shash_set5 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 79 10 79 43
+  let%span shash_set6 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 230 8 230 43
+  let%span shash_set7 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 210 8 210 38
+  let%span shash_set8 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 87 4 87 31
+  let%span shash_set9 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sseq10 = "../../../creusot-contracts/src/logic/seq.rs" 382 14 383 65
   let%span sseq11 = "../../../creusot-contracts/src/logic/seq.rs" 381 4 381 12
   let%span sfset12 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
@@ -2120,7 +2120,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 195 4 195 33] (self : t_Intersection'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 201 4 201 33] (self : t_Intersection'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -2147,7 +2147,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
    =
     [%#sseq14] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_Intersection'0) (visited : Seq.seq t_T'0) (end' : t_Intersection'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_Intersection'0) (visited : Seq.seq t_T'0) (end' : t_Intersection'0)
     
    =
     [%#shash_set9] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -2162,7 +2162,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 203 4 203 64] (self : t_Intersection'0) (visited : Seq.seq t_T'0) (o : t_Intersection'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 209 4 209 64] (self : t_Intersection'0) (visited : Seq.seq t_T'0) (o : t_Intersection'0)
     
    =
     [%#shash_set7] set_produces'0 self visited o
@@ -2176,7 +2176,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
   = contains'1 a x
   \/ contains'1 b x
   
-  function set_produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 74 0 80 1] (a : t_Intersection'0) (ab : Seq.seq t_T'0) (b : t_Intersection'0) (bc : Seq.seq t_T'0) (c : t_Intersection'0) : ()
+  function set_produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 80 0 86 1] (a : t_Intersection'0) (ab : Seq.seq t_T'0) (b : t_Intersection'0) (bc : Seq.seq t_T'0) (c : t_Intersection'0) : ()
     
    =
     [%#shash_set8] let _ = concat_contains'0 () in let _ = let _ = () in () in let _ = let _ = () in () in ()
@@ -2194,7 +2194,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
   
   constant c  : t_Intersection'0
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 223 4 223 90] (a : t_Intersection'0) (ab : Seq.seq t_T'0) (b : t_Intersection'0) (bc : Seq.seq t_T'0) (c : t_Intersection'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 229 4 229 90] (a : t_Intersection'0) (ab : Seq.seq t_T'0) (b : t_Intersection'0) (bc : Seq.seq t_T'0) (c : t_Intersection'0) : ()
     
   
   goal vc_produces_trans'0 : ([%#shash_set1] produces'0 b bc c)
@@ -4903,10 +4903,10 @@ module M_creusot_contracts__stdqy35z1__iter__cloned__qyi10472681371035856984__pr
   let%span scloned1 = "../../../creusot-contracts/src/std/iter/cloned.rs" 55 4 55 10
   let%span scloned2 = "../../../creusot-contracts/src/std/iter/cloned.rs" 48 12 51 79
   let%span scloned3 = "../../../creusot-contracts/src/std/iter/cloned.rs" 11 14 11 39
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -4940,16 +4940,16 @@ module M_creusot_contracts__stdqy35z1__iter__cloned__qyi10472681371035856984__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_T'0, b : t_I'0, bc : Seq.seq t_T'0, c : t_I'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_T'0) self
   
@@ -4983,10 +4983,10 @@ module M_creusot_contracts__stdqy35z1__iter__cloned__qyi10472681371035856984__pr
   let%span scloned3 = "../../../creusot-contracts/src/std/iter/cloned.rs" 60 4 60 10
   let%span scloned4 = "../../../creusot-contracts/src/std/iter/cloned.rs" 48 12 51 79
   let%span scloned5 = "../../../creusot-contracts/src/std/iter/cloned.rs" 11 14 11 39
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -5018,16 +5018,16 @@ module M_creusot_contracts__stdqy35z1__iter__cloned__qyi10472681371035856984__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_T'0, b : t_I'0, bc : Seq.seq t_T'0, c : t_I'0 . ([%#siter7] produces'1 a ab b)
    -> ([%#siter8] produces'1 b bc c)  -> ([%#siter9] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter6] produces'1 self (Seq.empty  : Seq.seq t_T'0) self
   
@@ -5071,10 +5071,10 @@ module M_creusot_contracts__stdqy35z1__iter__copied__qyi18224474876607687026__pr
   let%span scopied1 = "../../../creusot-contracts/src/std/iter/copied.rs" 55 4 55 10
   let%span scopied2 = "../../../creusot-contracts/src/std/iter/copied.rs" 48 12 51 79
   let%span scopied3 = "../../../creusot-contracts/src/std/iter/copied.rs" 11 14 11 39
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -5108,16 +5108,16 @@ module M_creusot_contracts__stdqy35z1__iter__copied__qyi18224474876607687026__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_T'0, b : t_I'0, bc : Seq.seq t_T'0, c : t_I'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_T'0) self
   
@@ -5151,10 +5151,10 @@ module M_creusot_contracts__stdqy35z1__iter__copied__qyi18224474876607687026__pr
   let%span scopied3 = "../../../creusot-contracts/src/std/iter/copied.rs" 60 4 60 10
   let%span scopied4 = "../../../creusot-contracts/src/std/iter/copied.rs" 48 12 51 79
   let%span scopied5 = "../../../creusot-contracts/src/std/iter/copied.rs" 11 14 11 39
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -5186,16 +5186,16 @@ module M_creusot_contracts__stdqy35z1__iter__copied__qyi18224474876607687026__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_T'0, b : t_I'0, bc : Seq.seq t_T'0, c : t_I'0 . ([%#siter7] produces'1 a ab b)
    -> ([%#siter8] produces'1 b bc c)  -> ([%#siter9] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter6] produces'1 self (Seq.empty  : Seq.seq t_T'0) self
   
@@ -5303,10 +5303,10 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   let%span senumerate1 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 80 4 80 10
   let%span senumerate2 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 72 12 76 113
   let%span senumerate3 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 14 14 14 39
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span senumerate8 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 45 12 49 85
   
   use seq.Seq
@@ -5334,16 +5334,16 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -5355,7 +5355,7 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   
   use prelude.prelude.Borrow
   
-  predicate completed'0 [#"../../../creusot-contracts/src/std/iter.rs" 35 4 35 36] (self : borrowed t_I'0)
+  predicate completed'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 36] (self : borrowed t_I'0)
   
   predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
   
@@ -5404,10 +5404,10 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   let%span senumerate3 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 85 4 85 10
   let%span senumerate4 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 72 12 76 113
   let%span senumerate5 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 14 14 14 39
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span senumerate10 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 45 12 49 85
   
   type t_I'0
@@ -5433,16 +5433,16 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter7] produces'1 a ab b)
    -> ([%#siter8] produces'1 b bc c)  -> ([%#siter9] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter6] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -5454,7 +5454,7 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   
   use prelude.prelude.Borrow
   
-  predicate completed'0 [#"../../../creusot-contracts/src/std/iter.rs" 35 4 35 36] (self : borrowed t_I'0)
+  predicate completed'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 36] (self : borrowed t_I'0)
   
   predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
   
@@ -5507,10 +5507,10 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   goal vc_produces_trans'0 : ([%#senumerate1] produces'0 b bc c)
    -> ([%#senumerate0] produces'0 a ab b)  -> ([%#senumerate2] produces'0 a (Seq.(++) ab bc) c)
 end
-module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__produces_refl [#"../../../creusot-contracts/src/std/iter/filter.rs" 106 4 106 26] (* <std::iter::Filter<I, F> as std::iter::Iterator> *)
-  let%span sfilter0 = "../../../creusot-contracts/src/std/iter/filter.rs" 105 14 105 45
-  let%span sfilter1 = "../../../creusot-contracts/src/std/iter/filter.rs" 103 4 103 10
-  let%span sfilter2 = "../../../creusot-contracts/src/std/iter/filter.rs" 87 12 99 17
+module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__produces_refl [#"../../../creusot-contracts/src/std/iter/filter.rs" 105 4 105 26] (* <std::iter::Filter<I, F> as std::iter::Iterator> *)
+  let%span sfilter0 = "../../../creusot-contracts/src/std/iter/filter.rs" 104 14 104 45
+  let%span sfilter1 = "../../../creusot-contracts/src/std/iter/filter.rs" 102 4 102 10
+  let%span sfilter2 = "../../../creusot-contracts/src/std/iter/filter.rs" 87 12 98 143
   let%span sfilter3 = "../../../creusot-contracts/src/std/iter/filter.rs" 34 12 40 124
   let%span sfilter4 = "../../../creusot-contracts/src/std/iter/filter.rs" 22 14 22 39
   let%span sfilter5 = "../../../creusot-contracts/src/std/iter/filter.rs" 15 14 15 39
@@ -5521,10 +5521,10 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops12 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -5607,16 +5607,16 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter14] produces'1 a ab b)
    -> ([%#siter15] produces'1 b bc c)  -> ([%#siter16] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter13] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -5632,8 +5632,8 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
     [%#sfilter2] invariant'0 self
      -> unnest'0 (func'0 self) (func'0 succ)
     /\ (exists s : Seq.seq t_Item'0, f : Map.map int int . produces'1 (iter'0 self) s (iter'0 succ)
-    /\ (forall i : int, j : int . 0 <= i /\ i <= j /\ j < Seq.length visited
-     -> 0 <= Map.get f i /\ Map.get f i <= Map.get f j /\ Map.get f j < Seq.length s)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
     /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> Seq.get visited i = Seq.get s (Map.get f i))
     /\ (forall i : int . 0 <= i /\ i < Seq.length s
      -> (exists j : int . 0 <= j /\ j < Seq.length visited /\ Map.get f j = i)
@@ -5641,16 +5641,16 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   
   constant self  : t_Filter'0
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 106 4 106 26] (self : t_Filter'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 105 4 105 26] (self : t_Filter'0) : ()
   
   goal vc_produces_refl'0 : [%#sfilter0] produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
 end
-module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__produces_trans [#"../../../creusot-contracts/src/std/iter/filter.rs" 113 4 113 90] (* <std::iter::Filter<I, F> as std::iter::Iterator> *)
-  let%span sfilter0 = "../../../creusot-contracts/src/std/iter/filter.rs" 110 15 110 32
-  let%span sfilter1 = "../../../creusot-contracts/src/std/iter/filter.rs" 111 15 111 32
-  let%span sfilter2 = "../../../creusot-contracts/src/std/iter/filter.rs" 112 14 112 42
-  let%span sfilter3 = "../../../creusot-contracts/src/std/iter/filter.rs" 108 4 108 10
-  let%span sfilter4 = "../../../creusot-contracts/src/std/iter/filter.rs" 87 12 99 17
+module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__produces_trans [#"../../../creusot-contracts/src/std/iter/filter.rs" 112 4 112 90] (* <std::iter::Filter<I, F> as std::iter::Iterator> *)
+  let%span sfilter0 = "../../../creusot-contracts/src/std/iter/filter.rs" 109 15 109 32
+  let%span sfilter1 = "../../../creusot-contracts/src/std/iter/filter.rs" 110 15 110 32
+  let%span sfilter2 = "../../../creusot-contracts/src/std/iter/filter.rs" 111 14 111 42
+  let%span sfilter3 = "../../../creusot-contracts/src/std/iter/filter.rs" 107 4 107 10
+  let%span sfilter4 = "../../../creusot-contracts/src/std/iter/filter.rs" 87 12 98 143
   let%span sfilter5 = "../../../creusot-contracts/src/std/iter/filter.rs" 34 12 40 124
   let%span sfilter6 = "../../../creusot-contracts/src/std/iter/filter.rs" 22 14 22 39
   let%span sfilter7 = "../../../creusot-contracts/src/std/iter/filter.rs" 15 14 15 39
@@ -5661,10 +5661,10 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   let%span sops12 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops13 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops14 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -5747,16 +5747,16 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter16] produces'1 a ab b)
    -> ([%#siter17] produces'1 b bc c)  -> ([%#siter18] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter15] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -5772,8 +5772,8 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
     [%#sfilter4] invariant'0 self
      -> unnest'0 (func'0 self) (func'0 succ)
     /\ (exists s : Seq.seq t_Item'0, f : Map.map int int . produces'1 (iter'0 self) s (iter'0 succ)
-    /\ (forall i : int, j : int . 0 <= i /\ i <= j /\ j < Seq.length visited
-     -> 0 <= Map.get f i /\ Map.get f i <= Map.get f j /\ Map.get f j < Seq.length s)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
     /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> Seq.get visited i = Seq.get s (Map.get f i))
     /\ (forall i : int . 0 <= i /\ i < Seq.length s
      -> (exists j : int . 0 <= j /\ j < Seq.length visited /\ Map.get f j = i)
@@ -5789,22 +5789,361 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   
   constant c  : t_Filter'0
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 113 4 113 90] (a : t_Filter'0) (ab : Seq.seq t_Item'0) (b : t_Filter'0) (bc : Seq.seq t_Item'0) (c : t_Filter'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 112 4 112 90] (a : t_Filter'0) (ab : Seq.seq t_Item'0) (b : t_Filter'0) (bc : Seq.seq t_Item'0) (c : t_Filter'0) : ()
     
   
   goal vc_produces_trans'0 : ([%#sfilter1] produces'0 b bc c)
    -> ([%#sfilter0] produces'0 a ab b)  -> ([%#sfilter2] produces'0 a (Seq.(++) ab bc) c)
 end
+module M_creusot_contracts__stdqy35z1__iter__filter_map__qyi13601925333174091585__produces_refl [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 105 4 105 26] (* <std::iter::FilterMap<I, F> as std::iter::Iterator> *)
+  let%span sfilter_map0 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 104 14 104 45
+  let%span sfilter_map1 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 102 4 102 10
+  let%span sfilter_map2 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 85 12 98 148
+  let%span sfilter_map3 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 34 12 38 32
+  let%span sfilter_map4 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 22 14 22 39
+  let%span sfilter_map5 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 15 14 15 39
+  let%span sfilter_map6 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 48 16 48 50
+  let%span sfilter_map7 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 56 16 56 52
+  let%span sfilter_map8 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 63 16 63 135
+  let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
+  let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 110 14 110 36
+  let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 115 14 115 31
+  let%span sops12 = "../../../creusot-contracts/src/std/ops.rs" 120 15 120 29
+  let%span sops13 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
+  let%span sops14 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
+  let%span sops15 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
+  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter19 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
+  
+  use seq.Seq
+  
+  type t_B'0
+  
+  use seq.Seq
+  
+  type t_I'0
+  
+  type t_F'0
+  
+  type t_FilterMap'0  =
+    { t_FilterMap__iter'0: t_I'0; t_FilterMap__f'0: t_F'0 }
+  
+  predicate inv'2 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
+  
+  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_F'0)
+  
+  type t_Item'0
+  
+  predicate precondition'0 [#"../../../creusot-contracts/src/std/ops.rs" 77 4 77 45] (self : t_F'0) (args : t_Item'0)
+  
+  predicate no_precondition'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 47 0 47 68] (f : t_F'0) =
+    [%#sfilter_map6] forall i : t_Item'0 . precondition'0 f (i)
+  
+  type t_Option'0  =
+    | C_None'0
+    | C_Some'0 t_B'0
+  
+  predicate postcondition_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 85 4 85 73] (self : t_F'0) (args : t_Item'0) (result : t_Option'0)
+    
+  
+  use prelude.prelude.Borrow
+  
+  predicate resolve'0 [#"../../../creusot-contracts/src/resolve.rs" 19 0 19 40] (_1 : t_F'0)
+  
+  predicate postcondition_mut'0 [#"../../../creusot-contracts/src/std/ops.rs" 95 4 95 92] (self : t_F'0) (args : t_Item'0) (result_state : t_F'0) (result : t_Option'0)
+    
+  
+  function fn_mut_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 129 4 129 55] (self : t_F'0) (args : t_Item'0) (res : t_Option'0) : ()
+    
+  
+  axiom fn_mut_once'0_spec : forall self : t_F'0, args : t_Item'0, res : t_Option'0 . [%#sops15] postcondition_once'0 self args res
+  = (exists res_state : t_F'0 . postcondition_mut'0 self args res_state res /\ resolve'0 res_state)
+  
+  predicate unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 103 4 103 36] (self : t_F'0) (_2 : t_F'0)
+  
+  function unnest_trans'0 [#"../../../creusot-contracts/src/std/ops.rs" 123 4 123 43] (self : t_F'0) (b : t_F'0) (c : t_F'0) : ()
+    
+  
+  axiom unnest_trans'0_spec : forall self : t_F'0, b : t_F'0, c : t_F'0 . ([%#sops12] unnest'0 self b)
+   -> ([%#sops13] unnest'0 b c)  -> ([%#sops14] unnest'0 self c)
+  
+  function unnest_refl'0 [#"../../../creusot-contracts/src/std/ops.rs" 116 4 116 24] (self : t_F'0) : ()
+  
+  axiom unnest_refl'0_spec : forall self : t_F'0 . [%#sops11] unnest'0 self self
+  
+  function postcondition_mut_unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 111 4 111 85] (self : t_F'0) (args : t_Item'0) (res_state : t_F'0) (res : t_Option'0) : ()
+    
+  
+  axiom postcondition_mut_unnest'0_spec : forall self : t_F'0, args : t_Item'0, res_state : t_F'0, res : t_Option'0 . ([%#sops9] postcondition_mut'0 self args res_state res)
+   -> ([%#sops10] unnest'0 self res_state)
+  
+  predicate immutable'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 55 0 55 62] (f : t_F'0) =
+    [%#sfilter_map7] forall g : t_F'0 . unnest'0 f g  -> f = g
+  
+  predicate precise'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 62 0 62 61] (f1 : t_F'0) =
+    [%#sfilter_map8] forall f2 : t_F'0, i : t_Item'0 . not ((exists b : t_B'0 . postcondition_mut'0 f1 (i) f2 (C_Some'0 b))
+    /\ postcondition_mut'0 f1 (i) f2 (C_None'0))
+  
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_FilterMap'0)
+  
+  function func'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 23 4 23 22] (self : t_FilterMap'0) : t_F'0
+  
+  axiom func'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map4] inv'0 self  -> inv'1 (func'0 self)
+  
+  predicate invariant'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 31 4 31 30] (self : t_FilterMap'0) =
+    [%#sfilter_map3] no_precondition'0 (func'0 self) /\ immutable'0 (func'0 self) /\ precise'0 (func'0 self)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_FilterMap'0 [inv'0 x] . inv'0 x
+  = (invariant'0 x
+  /\ match x with
+    | {t_FilterMap__iter'0 = iter ; t_FilterMap__f'0 = f} -> inv'2 iter /\ inv'1 f
+    end)
+  
+  use seq.Seq
+  
+  use prelude.prelude.Int
+  
+  use map.Map
+  
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 16 4 16 22] (self : t_FilterMap'0) : t_I'0
+  
+  axiom iter'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map5] inv'0 self  -> inv'2 (iter'0 self)
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+    
+  
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+    
+  
+  axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter17] produces'1 a ab b)
+   -> ([%#siter18] produces'1 b bc c)  -> ([%#siter19] produces'1 a (Seq.(++) ab bc) c)
+  
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
+  
+  axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter16] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
+  
+  use seq.Seq
+  
+  use map.Map
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 83 4 83 67] (self : t_FilterMap'0) (visited : Seq.seq t_B'0) (succ : t_FilterMap'0)
+    
+   =
+    [%#sfilter_map2] invariant'0 self
+     -> unnest'0 (func'0 self) (func'0 succ)
+    /\ (exists s : Seq.seq t_Item'0, f : Map.map int int . produces'1 (iter'0 self) s (iter'0 succ)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> postcondition_mut'0 (func'0 self) (Seq.get s (Map.get f i)) (func'0 self) (C_Some'0 (Seq.get visited i)))
+    /\ (forall j : int . 0 <= j /\ j < Seq.length s
+     -> (not (exists i : int . 0 <= i /\ i < Seq.length visited /\ Map.get f i = j))
+    = postcondition_mut'0 (func'0 self) (Seq.get s j) (func'0 self) (C_None'0)))
+  
+  constant self  : t_FilterMap'0
+  
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 105 4 105 26] (self : t_FilterMap'0) : ()
+    
+  
+  goal vc_produces_refl'0 : [%#sfilter_map0] produces'0 self (Seq.empty  : Seq.seq t_B'0) self
+end
+module M_creusot_contracts__stdqy35z1__iter__filter_map__qyi13601925333174091585__produces_trans [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 112 4 112 90] (* <std::iter::FilterMap<I, F> as std::iter::Iterator> *)
+  let%span sfilter_map0 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 109 15 109 32
+  let%span sfilter_map1 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 110 15 110 32
+  let%span sfilter_map2 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 111 14 111 42
+  let%span sfilter_map3 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 107 4 107 10
+  let%span sfilter_map4 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 85 12 98 148
+  let%span sfilter_map5 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 34 12 38 32
+  let%span sfilter_map6 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 22 14 22 39
+  let%span sfilter_map7 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 15 14 15 39
+  let%span sfilter_map8 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 48 16 48 50
+  let%span sfilter_map9 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 56 16 56 52
+  let%span sfilter_map10 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 63 16 63 135
+  let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
+  let%span sops12 = "../../../creusot-contracts/src/std/ops.rs" 110 14 110 36
+  let%span sops13 = "../../../creusot-contracts/src/std/ops.rs" 115 14 115 31
+  let%span sops14 = "../../../creusot-contracts/src/std/ops.rs" 120 15 120 29
+  let%span sops15 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
+  let%span sops16 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
+  let%span sops17 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
+  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter19 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter20 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter21 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
+  
+  type t_I'0
+  
+  type t_F'0
+  
+  type t_FilterMap'0  =
+    { t_FilterMap__iter'0: t_I'0; t_FilterMap__f'0: t_F'0 }
+  
+  type t_B'0
+  
+  use seq.Seq
+  
+  predicate inv'2 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
+  
+  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_F'0)
+  
+  type t_Item'0
+  
+  predicate precondition'0 [#"../../../creusot-contracts/src/std/ops.rs" 77 4 77 45] (self : t_F'0) (args : t_Item'0)
+  
+  predicate no_precondition'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 47 0 47 68] (f : t_F'0) =
+    [%#sfilter_map8] forall i : t_Item'0 . precondition'0 f (i)
+  
+  type t_Option'0  =
+    | C_None'0
+    | C_Some'0 t_B'0
+  
+  predicate postcondition_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 85 4 85 73] (self : t_F'0) (args : t_Item'0) (result : t_Option'0)
+    
+  
+  use prelude.prelude.Borrow
+  
+  predicate resolve'0 [#"../../../creusot-contracts/src/resolve.rs" 19 0 19 40] (_1 : t_F'0)
+  
+  predicate postcondition_mut'0 [#"../../../creusot-contracts/src/std/ops.rs" 95 4 95 92] (self : t_F'0) (args : t_Item'0) (result_state : t_F'0) (result : t_Option'0)
+    
+  
+  function fn_mut_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 129 4 129 55] (self : t_F'0) (args : t_Item'0) (res : t_Option'0) : ()
+    
+  
+  axiom fn_mut_once'0_spec : forall self : t_F'0, args : t_Item'0, res : t_Option'0 . [%#sops17] postcondition_once'0 self args res
+  = (exists res_state : t_F'0 . postcondition_mut'0 self args res_state res /\ resolve'0 res_state)
+  
+  predicate unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 103 4 103 36] (self : t_F'0) (_2 : t_F'0)
+  
+  function unnest_trans'0 [#"../../../creusot-contracts/src/std/ops.rs" 123 4 123 43] (self : t_F'0) (b : t_F'0) (c : t_F'0) : ()
+    
+  
+  axiom unnest_trans'0_spec : forall self : t_F'0, b : t_F'0, c : t_F'0 . ([%#sops14] unnest'0 self b)
+   -> ([%#sops15] unnest'0 b c)  -> ([%#sops16] unnest'0 self c)
+  
+  function unnest_refl'0 [#"../../../creusot-contracts/src/std/ops.rs" 116 4 116 24] (self : t_F'0) : ()
+  
+  axiom unnest_refl'0_spec : forall self : t_F'0 . [%#sops13] unnest'0 self self
+  
+  function postcondition_mut_unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 111 4 111 85] (self : t_F'0) (args : t_Item'0) (res_state : t_F'0) (res : t_Option'0) : ()
+    
+  
+  axiom postcondition_mut_unnest'0_spec : forall self : t_F'0, args : t_Item'0, res_state : t_F'0, res : t_Option'0 . ([%#sops11] postcondition_mut'0 self args res_state res)
+   -> ([%#sops12] unnest'0 self res_state)
+  
+  predicate immutable'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 55 0 55 62] (f : t_F'0) =
+    [%#sfilter_map9] forall g : t_F'0 . unnest'0 f g  -> f = g
+  
+  predicate precise'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 62 0 62 61] (f1 : t_F'0) =
+    [%#sfilter_map10] forall f2 : t_F'0, i : t_Item'0 . not ((exists b : t_B'0 . postcondition_mut'0 f1 (i) f2 (C_Some'0 b))
+    /\ postcondition_mut'0 f1 (i) f2 (C_None'0))
+  
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_FilterMap'0)
+  
+  function func'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 23 4 23 22] (self : t_FilterMap'0) : t_F'0
+  
+  axiom func'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map6] inv'0 self  -> inv'1 (func'0 self)
+  
+  predicate invariant'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 31 4 31 30] (self : t_FilterMap'0) =
+    [%#sfilter_map5] no_precondition'0 (func'0 self) /\ immutable'0 (func'0 self) /\ precise'0 (func'0 self)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_FilterMap'0 [inv'0 x] . inv'0 x
+  = (invariant'0 x
+  /\ match x with
+    | {t_FilterMap__iter'0 = iter ; t_FilterMap__f'0 = f} -> inv'2 iter /\ inv'1 f
+    end)
+  
+  use seq.Seq
+  
+  use prelude.prelude.Int
+  
+  use map.Map
+  
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 16 4 16 22] (self : t_FilterMap'0) : t_I'0
+  
+  axiom iter'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map7] inv'0 self  -> inv'2 (iter'0 self)
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+    
+  
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+    
+  
+  axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter19] produces'1 a ab b)
+   -> ([%#siter20] produces'1 b bc c)  -> ([%#siter21] produces'1 a (Seq.(++) ab bc) c)
+  
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
+  
+  axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter18] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
+  
+  use seq.Seq
+  
+  use map.Map
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 83 4 83 67] (self : t_FilterMap'0) (visited : Seq.seq t_B'0) (succ : t_FilterMap'0)
+    
+   =
+    [%#sfilter_map4] invariant'0 self
+     -> unnest'0 (func'0 self) (func'0 succ)
+    /\ (exists s : Seq.seq t_Item'0, f : Map.map int int . produces'1 (iter'0 self) s (iter'0 succ)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> postcondition_mut'0 (func'0 self) (Seq.get s (Map.get f i)) (func'0 self) (C_Some'0 (Seq.get visited i)))
+    /\ (forall j : int . 0 <= j /\ j < Seq.length s
+     -> (not (exists i : int . 0 <= i /\ i < Seq.length visited /\ Map.get f i = j))
+    = postcondition_mut'0 (func'0 self) (Seq.get s j) (func'0 self) (C_None'0)))
+  
+  use seq.Seq
+  
+  constant a  : t_FilterMap'0
+  
+  constant ab  : Seq.seq t_B'0
+  
+  constant b  : t_FilterMap'0
+  
+  constant bc  : Seq.seq t_B'0
+  
+  constant c  : t_FilterMap'0
+  
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 112 4 112 90] (a : t_FilterMap'0) (ab : Seq.seq t_B'0) (b : t_FilterMap'0) (bc : Seq.seq t_B'0) (c : t_FilterMap'0) : ()
+    
+  
+  goal vc_produces_trans'0 : ([%#sfilter_map1] produces'0 b bc c)
+   -> ([%#sfilter_map0] produces'0 a ab b)  -> ([%#sfilter_map2] produces'0 a (Seq.(++) ab bc) c)
+end
 module M_creusot_contracts__stdqy35z1__iter__fuse__qyi10730559947553418603__produces_refl [#"../../../creusot-contracts/src/std/iter/fuse.rs" 42 4 42 26] (* <std::iter::Fuse<I> as std::iter::Iterator> *)
   let%span sfuse0 = "../../../creusot-contracts/src/std/iter/fuse.rs" 41 14 41 45
   let%span sfuse1 = "../../../creusot-contracts/src/std/iter/fuse.rs" 39 4 39 10
   let%span sfuse2 = "../../../creusot-contracts/src/std/iter/fuse.rs" 29 12 35 13
   let%span sfuse3 = "../../../creusot-contracts/src/std/iter/fuse.rs" 8 14 8 39
   let%span sfuse4 = "../../../creusot-contracts/src/std/iter/fuse.rs" 9 14 9 71
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -5845,16 +6184,16 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi10730559947553418603__prod
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter6] produces'1 a ab b)
    -> ([%#siter7] produces'1 b bc c)  -> ([%#siter8] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter5] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -5883,10 +6222,10 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi10730559947553418603__prod
   let%span sfuse4 = "../../../creusot-contracts/src/std/iter/fuse.rs" 29 12 35 13
   let%span sfuse5 = "../../../creusot-contracts/src/std/iter/fuse.rs" 8 14 8 39
   let%span sfuse6 = "../../../creusot-contracts/src/std/iter/fuse.rs" 9 14 9 71
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -5927,16 +6266,16 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi10730559947553418603__prod
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter8] produces'1 a ab b)
    -> ([%#siter9] produces'1 b bc c)  -> ([%#siter10] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter7] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -5983,10 +6322,10 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi7691061398646472980__is_fu
   let%span smodel12 = "../../../creusot-contracts/src/model.rs" 110 8 110 22
   let%span sfuse13 = "../../../creusot-contracts/src/std/iter/fuse.rs" 8 14 8 39
   let%span sfuse14 = "../../../creusot-contracts/src/std/iter/fuse.rs" 9 14 9 71
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -6027,16 +6366,16 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi7691061398646472980__is_fu
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter16] produces'1 a ab b)
    -> ([%#siter17] produces'1 b bc c)  -> ([%#siter18] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter15] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -6069,7 +6408,7 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi7691061398646472980__is_fu
   function view'0 [#"../../../creusot-contracts/src/model.rs" 109 4 109 33] (self : borrowed (t_Fuse'0)) : t_Option'0 =
     [%#smodel12] view'1 self.current
   
-  predicate completed'1 [#"../../../creusot-contracts/src/std/iter.rs" 35 4 35 36] (self : borrowed t_I'0)
+  predicate completed'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 36] (self : borrowed t_I'0)
   
   predicate completed'0 [#"../../../creusot-contracts/src/std/iter/fuse.rs" 18 4 18 35] (self : borrowed (t_Fuse'0)) =
     [%#sfuse4] (view'0 self = C_None'0
@@ -6101,10 +6440,10 @@ module M_creusot_contracts__stdqy35z1__iter__map__qyi6597778842032428791__produc
   let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -6188,16 +6527,16 @@ module M_creusot_contracts__stdqy35z1__iter__map__qyi6597778842032428791__produc
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter13] produces'1 a ab b)
    -> ([%#siter14] produces'1 b bc c)  -> ([%#siter15] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter12] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -6250,10 +6589,10 @@ module M_creusot_contracts__stdqy35z1__iter__map__qyi6597778842032428791__produc
   let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops12 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops13 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -6335,16 +6674,16 @@ module M_creusot_contracts__stdqy35z1__iter__map__qyi6597778842032428791__produc
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter15] produces'1 a ab b)
    -> ([%#siter16] produces'1 b bc c)  -> ([%#siter17] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter14] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -6405,10 +6744,10 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi9026772487048432788__pr
   let%span sops7 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops8 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -6475,16 +6814,16 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi9026772487048432788__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter11] produces'1 a ab b)
    -> ([%#siter12] produces'1 b bc c)  -> ([%#siter13] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter10] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -6546,10 +6885,10 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi9026772487048432788__pr
   let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -6614,16 +6953,16 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi9026772487048432788__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter13] produces'1 a ab b)
    -> ([%#siter14] produces'1 b bc c)  -> ([%#siter15] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter12] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -6739,7 +7078,7 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4413682431414748756__ne
   let%span smap_inv6 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 90 17 90 21
   let%span smap_inv7 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 90 26 90 44
   let%span smap_inv8 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 86 14 89 5
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 162 27 162 52
   let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 163 26 163 71
   let%span smap_inv12 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 163 15 163 31
@@ -6763,10 +7102,10 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4413682431414748756__ne
   let%span smap_inv30 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 29 15 29 32
   let%span smap_inv31 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 30 14 30 42
   let%span smap_inv32 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 26 4 26 10
-  let%span siter33 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter34 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter35 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter36 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter33 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter34 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter35 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter36 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span sops37 = "../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
   let%span sops38 = "../../../creusot-contracts/src/std/ops.rs" 110 14 110 36
   let%span sops39 = "../../../creusot-contracts/src/std/ops.rs" 115 14 115 31
@@ -6822,20 +7161,20 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4413682431414748756__ne
   
   use seq.Seq
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter34] produces'0 a ab b)
    -> ([%#siter35] produces'0 b bc c)  -> ([%#siter36] produces'0 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter33] produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
   
-  predicate completed'1 [#"../../../creusot-contracts/src/std/iter.rs" 35 4 35 36] (self : borrowed t_I'0)
+  predicate completed'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 36] (self : borrowed t_I'0)
   
   use seq.Seq
   
@@ -7197,10 +7536,10 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4899712594723907874__pr
   let%span sops7 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops8 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -7254,16 +7593,16 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4899712594723907874__pr
   
   use seq.Seq
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter11] produces'0 a ab b)
    -> ([%#siter12] produces'0 b bc c)  -> ([%#siter13] produces'0 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter10] produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -7308,10 +7647,10 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4899712594723907874__pr
   let%span smap_inv6 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 29 15 29 32
   let%span smap_inv7 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 30 14 30 42
   let%span smap_inv8 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 26 4 26 10
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span sops13 = "../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
   let%span sops14 = "../../../creusot-contracts/src/std/ops.rs" 110 14 110 36
   let%span sops15 = "../../../creusot-contracts/src/std/ops.rs" 115 14 115 31
@@ -7389,16 +7728,16 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4899712594723907874__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter10] produces'1 a ab b)
    -> ([%#siter11] produces'1 b bc c)  -> ([%#siter12] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter9] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -7658,108 +7997,196 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi16860283617022118777__pro
   goal vc_produces_trans'0 : ([%#srange1] produces'0 b bc c)
    -> ([%#srange0] produces'0 a ab b)  -> ([%#srange2] produces'0 a (Seq.(++) ab bc) c)
 end
-module M_creusot_contracts__stdqy35z1__iter__range__range_inclusive_len [#"../../../creusot-contracts/src/std/iter/range.rs" 46 0 46 92]
-  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
-  let%span sops1 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
-  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
+module M_creusot_contracts__stdqy35z1__iter__range__qyi16137414346896623968__produces_back_refl [#"../../../creusot-contracts/src/std/iter/range.rs" 59 4 59 31] (* <std::ops::Range<Idx> as std::iter::DoubleEndedIterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 58 14 58 50
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 56 4 56 10
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 48 12 52 68
+  
+  use seq.Seq
   
   type t_Idx'0
   
-  type t_RangeInclusive'0  =
-    { t_RangeInclusive__start'0: t_Idx'0; t_RangeInclusive__end'0: t_Idx'0; t_RangeInclusive__exhausted'0: bool }
+  use seq.Seq
   
-  function start_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 193 4 193 29] (self : t_RangeInclusive'0) : t_Idx'0
+  type t_Range'0  =
+    { t_Range__start'0: t_Idx'0; t_Range__end'0: t_Idx'0 }
   
   use prelude.prelude.Int
   
   function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
   
-  function end_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 199 4 199 27] (self : t_RangeInclusive'0) : t_Idx'0
+  use seq.Seq
   
-  function is_empty_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 206 4 209 35] (self : t_RangeInclusive'0) : bool
+  use seq.Seq
   
-  axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops1] not is_empty_log'0 self
-   -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 46 4 46 69] (self : t_Range'0) (visited : Seq.seq t_Idx'0) (o : t_Range'0)
+    
+   =
+    [%#srange2] self.t_Range__start'0 = o.t_Range__start'0
+    /\ deep_model'0 self.t_Range__end'0 >= deep_model'0 o.t_Range__end'0
+    /\ (Seq.length visited > 0  -> deep_model'0 o.t_Range__end'0 >= deep_model'0 o.t_Range__start'0)
+    /\ Seq.length visited = deep_model'0 o.t_Range__end'0 - deep_model'0 self.t_Range__end'0
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> deep_model'0 (Seq.get visited i) = deep_model'0 self.t_Range__end'0 - i)
   
-  constant r  : t_RangeInclusive'0
+  constant self  : t_Range'0
   
-  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 46 0 46 92] (r : t_RangeInclusive'0) : int
-    
+  function produces_back_refl'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 59 4 59 31] (self : t_Range'0) : ()
   
-  goal vc_range_inclusive_len'0 : ([%#sops1] not is_empty_log'0 r
-   -> deep_model'0 (start_log'0 r) <= deep_model'0 (end_log'0 r))
-   -> (if is_empty_log'0 r then
-    [%#srange0] is_empty_log'0 r = (0 = 0)
-  else
-    [%#srange0] is_empty_log'0 r = (deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1 = 0)
-  )
+  goal vc_produces_back_refl'0 : [%#srange0] produces_back'0 self (Seq.empty  : Seq.seq t_Idx'0) self
 end
-module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__produces_refl [#"../../../creusot-contracts/src/std/iter/range.rs" 77 4 77 26] (* <std::ops::RangeInclusive<Idx> as std::iter::Iterator> *)
-  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
-  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
-  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 66 12 70 76
-  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
-  let%span srange4 = "../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
-  let%span sops5 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
-  
-  use seq.Seq
+module M_creusot_contracts__stdqy35z1__iter__range__qyi16137414346896623968__produces_back_trans [#"../../../creusot-contracts/src/std/iter/range.rs" 66 4 66 95] (* <std::ops::Range<Idx> as std::iter::DoubleEndedIterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 63 15 63 37
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 64 15 64 37
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 65 14 65 47
+  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 61 4 61 10
+  let%span srange4 = "../../../creusot-contracts/src/std/iter/range.rs" 48 12 52 68
   
   type t_Idx'0
   
-  use seq.Seq
-  
-  type t_RangeInclusive'0  =
-    { t_RangeInclusive__start'0: t_Idx'0; t_RangeInclusive__end'0: t_Idx'0; t_RangeInclusive__exhausted'0: bool }
+  type t_Range'0  =
+    { t_Range__start'0: t_Idx'0; t_Range__end'0: t_Idx'0 }
   
   use seq.Seq
   
-  function start_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 193 4 193 29] (self : t_RangeInclusive'0) : t_Idx'0
-  
   use prelude.prelude.Int
   
   function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
   
-  function end_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 199 4 199 27] (self : t_RangeInclusive'0) : t_Idx'0
-  
-  function is_empty_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 206 4 209 35] (self : t_RangeInclusive'0) : bool
-  
-  axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops5] not is_empty_log'0 self
-   -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
-  
-  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 46 0 46 92] (r : t_RangeInclusive'0) : int
-    
-   =
-    [%#srange4] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
-  
-  axiom range_inclusive_len'0_spec : forall r : t_RangeInclusive'0 . [%#srange3] is_empty_log'0 r
-  = (range_inclusive_len'0 r = 0)
+  use seq.Seq
   
   use seq.Seq
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 64 4 64 64] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 46 4 46 69] (self : t_Range'0) (visited : Seq.seq t_Idx'0) (o : t_Range'0)
     
    =
-    [%#srange2] Seq.length visited = range_inclusive_len'0 self - range_inclusive_len'0 o
-    /\ (is_empty_log'0 self  -> is_empty_log'0 o)
-    /\ (is_empty_log'0 o \/ end_log'0 self = end_log'0 o)
+    [%#srange4] self.t_Range__start'0 = o.t_Range__start'0
+    /\ deep_model'0 self.t_Range__end'0 >= deep_model'0 o.t_Range__end'0
+    /\ (Seq.length visited > 0  -> deep_model'0 o.t_Range__end'0 >= deep_model'0 o.t_Range__start'0)
+    /\ Seq.length visited = deep_model'0 o.t_Range__end'0 - deep_model'0 self.t_Range__end'0
     /\ (forall i : int . 0 <= i /\ i < Seq.length visited
-     -> deep_model'0 (Seq.get visited i) = deep_model'0 (start_log'0 self) + i)
+     -> deep_model'0 (Seq.get visited i) = deep_model'0 self.t_Range__end'0 - i)
   
-  constant self  : t_RangeInclusive'0
+  use seq.Seq
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 77 4 77 26] (self : t_RangeInclusive'0) : ()
+  constant a  : t_Range'0
+  
+  constant ab  : Seq.seq t_Idx'0
+  
+  constant b  : t_Range'0
+  
+  constant bc  : Seq.seq t_Idx'0
+  
+  constant c  : t_Range'0
+  
+  function produces_back_trans'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 66 4 66 95] (a : t_Range'0) (ab : Seq.seq t_Idx'0) (b : t_Range'0) (bc : Seq.seq t_Idx'0) (c : t_Range'0) : ()
+    
+  
+  goal vc_produces_back_trans'0 : ([%#srange1] produces_back'0 b bc c)
+   -> ([%#srange0] produces_back'0 a ab b)  -> ([%#srange2] produces_back'0 a (Seq.(++) ab bc) c)
+end
+module M_creusot_contracts__stdqy35z1__iter__range__range_inclusive_len [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92]
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span sops1 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
+  
+  type t_Idx'0
+  
+  type t_RangeInclusive'0  =
+    { t_RangeInclusive__start'0: t_Idx'0; t_RangeInclusive__end'0: t_Idx'0; t_RangeInclusive__exhausted'0: bool }
+  
+  function start_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 193 4 193 29] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  use prelude.prelude.Int
+  
+  function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
+  
+  function end_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 199 4 199 27] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  function is_empty_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 206 4 209 35] (self : t_RangeInclusive'0) : bool
+  
+  axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops1] not is_empty_log'0 self
+   -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
+  
+  constant r  : t_RangeInclusive'0
+  
+  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92] (r : t_RangeInclusive'0) : int
+    
+  
+  goal vc_range_inclusive_len'0 : ([%#sops1] not is_empty_log'0 r
+   -> deep_model'0 (start_log'0 r) <= deep_model'0 (end_log'0 r))
+   -> (if is_empty_log'0 r then
+    [%#srange0] is_empty_log'0 r = (0 = 0)
+  else
+    [%#srange0] is_empty_log'0 r = (deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1 = 0)
+  )
+end
+module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__produces_refl [#"../../../creusot-contracts/src/std/iter/range.rs" 103 4 103 26] (* <std::ops::RangeInclusive<Idx> as std::iter::Iterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 102 14 102 45
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 100 4 100 10
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 92 12 96 76
+  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange4 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
+  let%span sops5 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
+  
+  use seq.Seq
+  
+  type t_Idx'0
+  
+  use seq.Seq
+  
+  type t_RangeInclusive'0  =
+    { t_RangeInclusive__start'0: t_Idx'0; t_RangeInclusive__end'0: t_Idx'0; t_RangeInclusive__exhausted'0: bool }
+  
+  use seq.Seq
+  
+  function start_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 193 4 193 29] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  use prelude.prelude.Int
+  
+  function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
+  
+  function end_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 199 4 199 27] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  function is_empty_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 206 4 209 35] (self : t_RangeInclusive'0) : bool
+  
+  axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops5] not is_empty_log'0 self
+   -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
+  
+  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92] (r : t_RangeInclusive'0) : int
+    
+   =
+    [%#srange4] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
+  
+  axiom range_inclusive_len'0_spec : forall r : t_RangeInclusive'0 . [%#srange3] is_empty_log'0 r
+  = (range_inclusive_len'0 r = 0)
+  
+  use seq.Seq
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 90 4 90 64] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
+    
+   =
+    [%#srange2] Seq.length visited = range_inclusive_len'0 self - range_inclusive_len'0 o
+    /\ (is_empty_log'0 self  -> is_empty_log'0 o)
+    /\ (is_empty_log'0 o \/ end_log'0 self = end_log'0 o)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> deep_model'0 (Seq.get visited i) = deep_model'0 (start_log'0 self) + i)
+  
+  constant self  : t_RangeInclusive'0
+  
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 103 4 103 26] (self : t_RangeInclusive'0) : ()
     
   
   goal vc_produces_refl'0 : [%#srange0] produces'0 self (Seq.empty  : Seq.seq t_Idx'0) self
 end
-module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__produces_trans [#"../../../creusot-contracts/src/std/iter/range.rs" 84 4 84 90] (* <std::ops::RangeInclusive<Idx> as std::iter::Iterator> *)
-  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
-  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
-  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
-  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
-  let%span srange4 = "../../../creusot-contracts/src/std/iter/range.rs" 66 12 70 76
-  let%span srange5 = "../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
-  let%span srange6 = "../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
+module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__produces_trans [#"../../../creusot-contracts/src/std/iter/range.rs" 110 4 110 90] (* <std::ops::RangeInclusive<Idx> as std::iter::Iterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 107 15 107 32
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 108 15 108 32
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 109 14 109 42
+  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 105 4 105 10
+  let%span srange4 = "../../../creusot-contracts/src/std/iter/range.rs" 92 12 96 76
+  let%span srange5 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange6 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
   let%span sops7 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
   
   type t_Idx'0
@@ -7784,7 +8211,7 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__pro
   axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops7] not is_empty_log'0 self
    -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
   
-  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 46 0 46 92] (r : t_RangeInclusive'0) : int
+  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92] (r : t_RangeInclusive'0) : int
     
    =
     [%#srange6] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
@@ -7794,7 +8221,7 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__pro
   
   use seq.Seq
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 64 4 64 64] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 90 4 90 64] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
     
    =
     [%#srange4] Seq.length visited = range_inclusive_len'0 self - range_inclusive_len'0 o
@@ -7815,12 +8242,139 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__pro
   
   constant c  : t_RangeInclusive'0
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 84 4 84 90] (a : t_RangeInclusive'0) (ab : Seq.seq t_Idx'0) (b : t_RangeInclusive'0) (bc : Seq.seq t_Idx'0) (c : t_RangeInclusive'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 110 4 110 90] (a : t_RangeInclusive'0) (ab : Seq.seq t_Idx'0) (b : t_RangeInclusive'0) (bc : Seq.seq t_Idx'0) (c : t_RangeInclusive'0) : ()
     
   
   goal vc_produces_trans'0 : ([%#srange1] produces'0 b bc c)
    -> ([%#srange0] produces'0 a ab b)  -> ([%#srange2] produces'0 a (Seq.(++) ab bc) c)
 end
+module M_creusot_contracts__stdqy35z1__iter__range__qyi12106466433038921999__produces_back_refl [#"../../../creusot-contracts/src/std/iter/range.rs" 129 4 129 31] (* <std::ops::RangeInclusive<Idx> as std::iter::DoubleEndedIterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 128 14 128 50
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 126 4 126 10
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 118 12 122 74
+  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange4 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
+  let%span sops5 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
+  
+  use seq.Seq
+  
+  type t_Idx'0
+  
+  use seq.Seq
+  
+  type t_RangeInclusive'0  =
+    { t_RangeInclusive__start'0: t_Idx'0; t_RangeInclusive__end'0: t_Idx'0; t_RangeInclusive__exhausted'0: bool }
+  
+  use seq.Seq
+  
+  function start_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 193 4 193 29] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  use prelude.prelude.Int
+  
+  function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
+  
+  function end_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 199 4 199 27] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  function is_empty_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 206 4 209 35] (self : t_RangeInclusive'0) : bool
+  
+  axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops5] not is_empty_log'0 self
+   -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
+  
+  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92] (r : t_RangeInclusive'0) : int
+    
+   =
+    [%#srange4] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
+  
+  axiom range_inclusive_len'0_spec : forall r : t_RangeInclusive'0 . [%#srange3] is_empty_log'0 r
+  = (range_inclusive_len'0 r = 0)
+  
+  use seq.Seq
+  
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 116 4 116 69] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
+    
+   =
+    [%#srange2] Seq.length visited = range_inclusive_len'0 self - range_inclusive_len'0 o
+    /\ (is_empty_log'0 self  -> is_empty_log'0 o)
+    /\ (is_empty_log'0 o \/ start_log'0 self = start_log'0 o)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> deep_model'0 (Seq.get visited i) = deep_model'0 (end_log'0 self) - i)
+  
+  constant self  : t_RangeInclusive'0
+  
+  function produces_back_refl'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 129 4 129 31] (self : t_RangeInclusive'0) : ()
+    
+  
+  goal vc_produces_back_refl'0 : [%#srange0] produces_back'0 self (Seq.empty  : Seq.seq t_Idx'0) self
+end
+module M_creusot_contracts__stdqy35z1__iter__range__qyi12106466433038921999__produces_back_trans [#"../../../creusot-contracts/src/std/iter/range.rs" 136 4 136 95] (* <std::ops::RangeInclusive<Idx> as std::iter::DoubleEndedIterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 133 15 133 37
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 134 15 134 37
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 135 14 135 47
+  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 131 4 131 10
+  let%span srange4 = "../../../creusot-contracts/src/std/iter/range.rs" 118 12 122 74
+  let%span srange5 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange6 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
+  let%span sops7 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
+  
+  type t_Idx'0
+  
+  type t_RangeInclusive'0  =
+    { t_RangeInclusive__start'0: t_Idx'0; t_RangeInclusive__end'0: t_Idx'0; t_RangeInclusive__exhausted'0: bool }
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  function start_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 193 4 193 29] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  use prelude.prelude.Int
+  
+  function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
+  
+  function end_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 199 4 199 27] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  function is_empty_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 206 4 209 35] (self : t_RangeInclusive'0) : bool
+  
+  axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops7] not is_empty_log'0 self
+   -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
+  
+  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92] (r : t_RangeInclusive'0) : int
+    
+   =
+    [%#srange6] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
+  
+  axiom range_inclusive_len'0_spec : forall r : t_RangeInclusive'0 . [%#srange5] is_empty_log'0 r
+  = (range_inclusive_len'0 r = 0)
+  
+  use seq.Seq
+  
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 116 4 116 69] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
+    
+   =
+    [%#srange4] Seq.length visited = range_inclusive_len'0 self - range_inclusive_len'0 o
+    /\ (is_empty_log'0 self  -> is_empty_log'0 o)
+    /\ (is_empty_log'0 o \/ start_log'0 self = start_log'0 o)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> deep_model'0 (Seq.get visited i) = deep_model'0 (end_log'0 self) - i)
+  
+  use seq.Seq
+  
+  constant a  : t_RangeInclusive'0
+  
+  constant ab  : Seq.seq t_Idx'0
+  
+  constant b  : t_RangeInclusive'0
+  
+  constant bc  : Seq.seq t_Idx'0
+  
+  constant c  : t_RangeInclusive'0
+  
+  function produces_back_trans'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 136 4 136 95] (a : t_RangeInclusive'0) (ab : Seq.seq t_Idx'0) (b : t_RangeInclusive'0) (bc : Seq.seq t_Idx'0) (c : t_RangeInclusive'0) : ()
+    
+  
+  goal vc_produces_back_trans'0 : ([%#srange1] produces_back'0 b bc c)
+   -> ([%#srange0] produces_back'0 a ab b)  -> ([%#srange2] produces_back'0 a (Seq.(++) ab bc) c)
+end
 module M_creusot_contracts__stdqy35z1__iter__repeat__qyi8658929399712466629__produces_refl [#"../../../creusot-contracts/src/std/iter/repeat.rs" 32 4 32 26] (* <std::iter::Repeat<T> as std::iter::Iterator> *)
   let%span srepeat0 = "../../../creusot-contracts/src/std/iter/repeat.rs" 31 14 31 45
   let%span srepeat1 = "../../../creusot-contracts/src/std/iter/repeat.rs" 29 4 29 10
@@ -7899,16 +8453,15 @@ module M_creusot_contracts__stdqy35z1__iter__repeat__qyi8658929399712466629__pro
   goal vc_produces_trans'0 : ([%#srepeat1] produces'0 b bc c)
    -> ([%#srepeat0] produces'0 a ab b)  -> ([%#srepeat2] produces'0 a (Seq.(++) ab bc) c)
 end
-module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produces_refl [#"../../../creusot-contracts/src/std/iter/skip.rs" 74 4 74 26] (* <std::iter::Skip<I> as std::iter::Iterator> *)
-  let%span sskip0 = "../../../creusot-contracts/src/std/iter/skip.rs" 73 14 73 45
-  let%span sskip1 = "../../../creusot-contracts/src/std/iter/skip.rs" 71 4 71 10
-  let%span sskip2 = "../../../creusot-contracts/src/std/iter/skip.rs" 62 12 67 74
-  let%span sskip3 = "../../../creusot-contracts/src/std/iter/skip.rs" 21 14 21 50
-  let%span sskip4 = "../../../creusot-contracts/src/std/iter/skip.rs" 14 14 14 39
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+module M_creusot_contracts__stdqy35z1__iter__rev__qyi4378764544541057436__produces_refl [#"../../../creusot-contracts/src/std/iter/rev.rs" 48 4 48 26] (* <std::iter::Rev<I> as std::iter::Iterator> *)
+  let%span srev0 = "../../../creusot-contracts/src/std/iter/rev.rs" 47 14 47 45
+  let%span srev1 = "../../../creusot-contracts/src/std/iter/rev.rs" 45 4 45 10
+  let%span srev2 = "../../../creusot-contracts/src/std/iter/rev.rs" 41 12 41 56
+  let%span srev3 = "../../../creusot-contracts/src/std/iter/rev.rs" 17 14 17 39
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 106 14 106 50
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 110 15 110 37
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 111 15 111 37
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 112 14 112 47
   
   use seq.Seq
   
@@ -7918,106 +8471,239 @@ module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produ
   
   type t_I'0
   
-  use prelude.prelude.UIntSize
-  
-  type t_Skip'0  =
-    { t_Skip__iter'0: t_I'0; t_Skip__n'0: usize }
-  
-  use prelude.prelude.Int
-  
-  constant v_MAX'0 : usize = (18446744073709551615 : usize)
-  
-  use prelude.prelude.UIntSize
-  
-  function n'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 22 4 22 21] (self : t_Skip'0) : int
-  
-  axiom n'0_spec : forall self : t_Skip'0 . [%#sskip3] n'0 self >= 0 /\ n'0 self <= UIntSize.to_int (v_MAX'0 : usize)
-  
-  use seq.Seq
+  type t_Rev'0  =
+    { t_Rev__iter'0: t_I'0 }
   
   predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
   
-  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Skip'0)
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Rev'0)
   
-  axiom inv_axiom'0 [@rewrite] : forall x : t_Skip'0 [inv'0 x] . inv'0 x
+  axiom inv_axiom'0 [@rewrite] : forall x : t_Rev'0 [inv'0 x] . inv'0 x
   = match x with
-    | {t_Skip__iter'0 = iter ; t_Skip__n'0 = n} -> inv'1 iter
+    | {t_Rev__iter'0 = iter} -> inv'1 iter
     end
   
-  function iter'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 15 4 15 22] (self : t_Skip'0) : t_I'0
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 18 4 18 22] (self : t_Rev'0) : t_I'0
   
-  axiom iter'0_spec : forall self : t_Skip'0 . [%#sskip4] inv'0 self  -> inv'1 (iter'0 self)
+  axiom iter'0_spec : forall self : t_Rev'0 . [%#srev3] inv'0 self  -> inv'1 (iter'0 self)
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter.rs" 103 4 103 70] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_back_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 113 4 113 96] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
-  axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter6] produces'1 a ab b)
-   -> ([%#siter7] produces'1 b bc c)  -> ([%#siter8] produces'1 a (Seq.(++) ab bc) c)
-  
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
-  
-  axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter5] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
-  
-  use seq.Seq
+  axiom produces_back_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter5] produces_back'0 a ab b)
+   -> ([%#siter6] produces_back'0 b bc c)  -> ([%#siter7] produces_back'0 a (Seq.(++) ab bc) c)
   
-  use prelude.prelude.Borrow
+  function produces_back_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 107 4 107 32] (self : t_I'0) : ()
   
-  predicate resolve'0 [#"../../../creusot-contracts/src/resolve.rs" 19 0 19 40] (_1 : t_Item'0)
+  axiom produces_back_refl'0_spec : forall self : t_I'0 . [%#siter4] produces_back'0 self (Seq.empty  : Seq.seq t_Item'0) self
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 60 4 60 64] (self : t_Skip'0) (visited : Seq.seq t_Item'0) (o : t_Skip'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 39 4 39 64] (self : t_Rev'0) (visited : Seq.seq t_Item'0) (o : t_Rev'0)
     
    =
-    [%#sskip2] visited = (Seq.empty  : Seq.seq t_Item'0) /\ self = o
-    \/ n'0 o = 0
-    /\ Seq.length visited > 0
-    /\ (exists s : Seq.seq t_Item'0 . Seq.length s = n'0 self
-    /\ produces'1 (iter'0 self) (Seq.(++) s visited) (iter'0 o)
-    /\ (forall i : int . 0 <= i /\ i < Seq.length s  -> resolve'0 (Seq.get s i)))
+    [%#srev2] produces_back'0 (iter'0 self) visited (iter'0 o)
   
-  constant self  : t_Skip'0
+  constant self  : t_Rev'0
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 74 4 74 26] (self : t_Skip'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 48 4 48 26] (self : t_Rev'0) : ()
   
-  goal vc_produces_refl'0 : [%#sskip0] produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
+  goal vc_produces_refl'0 : [%#srev0] produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
 end
-module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produces_trans [#"../../../creusot-contracts/src/std/iter/skip.rs" 81 4 81 90] (* <std::iter::Skip<I> as std::iter::Iterator> *)
-  let%span sskip0 = "../../../creusot-contracts/src/std/iter/skip.rs" 78 15 78 32
-  let%span sskip1 = "../../../creusot-contracts/src/std/iter/skip.rs" 79 15 79 32
-  let%span sskip2 = "../../../creusot-contracts/src/std/iter/skip.rs" 80 14 80 42
-  let%span sskip3 = "../../../creusot-contracts/src/std/iter/skip.rs" 76 4 76 10
-  let%span sskip4 = "../../../creusot-contracts/src/std/iter/skip.rs" 62 12 67 74
-  let%span sskip5 = "../../../creusot-contracts/src/std/iter/skip.rs" 21 14 21 50
-  let%span sskip6 = "../../../creusot-contracts/src/std/iter/skip.rs" 14 14 14 39
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+module M_creusot_contracts__stdqy35z1__iter__rev__qyi4378764544541057436__produces_trans [#"../../../creusot-contracts/src/std/iter/rev.rs" 55 4 55 90] (* <std::iter::Rev<I> as std::iter::Iterator> *)
+  let%span srev0 = "../../../creusot-contracts/src/std/iter/rev.rs" 52 15 52 32
+  let%span srev1 = "../../../creusot-contracts/src/std/iter/rev.rs" 53 15 53 32
+  let%span srev2 = "../../../creusot-contracts/src/std/iter/rev.rs" 54 14 54 42
+  let%span srev3 = "../../../creusot-contracts/src/std/iter/rev.rs" 50 4 50 10
+  let%span srev4 = "../../../creusot-contracts/src/std/iter/rev.rs" 41 12 41 56
+  let%span srev5 = "../../../creusot-contracts/src/std/iter/rev.rs" 17 14 17 39
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 106 14 106 50
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 110 15 110 37
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 111 15 111 37
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 112 14 112 47
   
   type t_I'0
   
-  use prelude.prelude.UIntSize
-  
-  type t_Skip'0  =
-    { t_Skip__iter'0: t_I'0; t_Skip__n'0: usize }
+  type t_Rev'0  =
+    { t_Rev__iter'0: t_I'0 }
   
   type t_Item'0
   
   use seq.Seq
   
-  use seq.Seq
+  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
   
-  use prelude.prelude.Int
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Rev'0)
   
-  constant v_MAX'0 : usize = (18446744073709551615 : usize)
+  axiom inv_axiom'0 [@rewrite] : forall x : t_Rev'0 [inv'0 x] . inv'0 x
+  = match x with
+    | {t_Rev__iter'0 = iter} -> inv'1 iter
+    end
   
-  use prelude.prelude.UIntSize
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 18 4 18 22] (self : t_Rev'0) : t_I'0
   
-  function n'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 22 4 22 21] (self : t_Skip'0) : int
+  axiom iter'0_spec : forall self : t_Rev'0 . [%#srev5] inv'0 self  -> inv'1 (iter'0 self)
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter.rs" 103 4 103 70] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+    
+  
+  function produces_back_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 113 4 113 96] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+    
+  
+  axiom produces_back_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter7] produces_back'0 a ab b)
+   -> ([%#siter8] produces_back'0 b bc c)  -> ([%#siter9] produces_back'0 a (Seq.(++) ab bc) c)
+  
+  function produces_back_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 107 4 107 32] (self : t_I'0) : ()
+  
+  axiom produces_back_refl'0_spec : forall self : t_I'0 . [%#siter6] produces_back'0 self (Seq.empty  : Seq.seq t_Item'0) self
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 39 4 39 64] (self : t_Rev'0) (visited : Seq.seq t_Item'0) (o : t_Rev'0)
+    
+   =
+    [%#srev4] produces_back'0 (iter'0 self) visited (iter'0 o)
+  
+  constant a  : t_Rev'0
+  
+  constant ab  : Seq.seq t_Item'0
+  
+  constant b  : t_Rev'0
+  
+  constant bc  : Seq.seq t_Item'0
+  
+  constant c  : t_Rev'0
+  
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 55 4 55 90] (a : t_Rev'0) (ab : Seq.seq t_Item'0) (b : t_Rev'0) (bc : Seq.seq t_Item'0) (c : t_Rev'0) : ()
+    
+  
+  goal vc_produces_trans'0 : ([%#srev1] produces'0 b bc c)
+   -> ([%#srev0] produces'0 a ab b)  -> ([%#srev2] produces'0 a (Seq.(++) ab bc) c)
+end
+module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produces_refl [#"../../../creusot-contracts/src/std/iter/skip.rs" 74 4 74 26] (* <std::iter::Skip<I> as std::iter::Iterator> *)
+  let%span sskip0 = "../../../creusot-contracts/src/std/iter/skip.rs" 73 14 73 45
+  let%span sskip1 = "../../../creusot-contracts/src/std/iter/skip.rs" 71 4 71 10
+  let%span sskip2 = "../../../creusot-contracts/src/std/iter/skip.rs" 62 12 67 74
+  let%span sskip3 = "../../../creusot-contracts/src/std/iter/skip.rs" 21 14 21 50
+  let%span sskip4 = "../../../creusot-contracts/src/std/iter/skip.rs" 14 14 14 39
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
+  
+  use seq.Seq
+  
+  type t_Item'0
+  
+  use seq.Seq
+  
+  type t_I'0
+  
+  use prelude.prelude.UIntSize
+  
+  type t_Skip'0  =
+    { t_Skip__iter'0: t_I'0; t_Skip__n'0: usize }
+  
+  use prelude.prelude.Int
+  
+  constant v_MAX'0 : usize = (18446744073709551615 : usize)
+  
+  use prelude.prelude.UIntSize
+  
+  function n'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 22 4 22 21] (self : t_Skip'0) : int
+  
+  axiom n'0_spec : forall self : t_Skip'0 . [%#sskip3] n'0 self >= 0 /\ n'0 self <= UIntSize.to_int (v_MAX'0 : usize)
+  
+  use seq.Seq
+  
+  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
+  
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Skip'0)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_Skip'0 [inv'0 x] . inv'0 x
+  = match x with
+    | {t_Skip__iter'0 = iter ; t_Skip__n'0 = n} -> inv'1 iter
+    end
+  
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 15 4 15 22] (self : t_Skip'0) : t_I'0
+  
+  axiom iter'0_spec : forall self : t_Skip'0 . [%#sskip4] inv'0 self  -> inv'1 (iter'0 self)
+  
+  use seq.Seq
+  
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+    
+  
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+    
+  
+  axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter6] produces'1 a ab b)
+   -> ([%#siter7] produces'1 b bc c)  -> ([%#siter8] produces'1 a (Seq.(++) ab bc) c)
+  
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
+  
+  axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter5] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
+  
+  use seq.Seq
+  
+  use prelude.prelude.Borrow
+  
+  predicate resolve'0 [#"../../../creusot-contracts/src/resolve.rs" 19 0 19 40] (_1 : t_Item'0)
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 60 4 60 64] (self : t_Skip'0) (visited : Seq.seq t_Item'0) (o : t_Skip'0)
+    
+   =
+    [%#sskip2] visited = (Seq.empty  : Seq.seq t_Item'0) /\ self = o
+    \/ n'0 o = 0
+    /\ Seq.length visited > 0
+    /\ (exists s : Seq.seq t_Item'0 . Seq.length s = n'0 self
+    /\ produces'1 (iter'0 self) (Seq.(++) s visited) (iter'0 o)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length s  -> resolve'0 (Seq.get s i)))
+  
+  constant self  : t_Skip'0
+  
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 74 4 74 26] (self : t_Skip'0) : ()
+  
+  goal vc_produces_refl'0 : [%#sskip0] produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
+end
+module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produces_trans [#"../../../creusot-contracts/src/std/iter/skip.rs" 81 4 81 90] (* <std::iter::Skip<I> as std::iter::Iterator> *)
+  let%span sskip0 = "../../../creusot-contracts/src/std/iter/skip.rs" 78 15 78 32
+  let%span sskip1 = "../../../creusot-contracts/src/std/iter/skip.rs" 79 15 79 32
+  let%span sskip2 = "../../../creusot-contracts/src/std/iter/skip.rs" 80 14 80 42
+  let%span sskip3 = "../../../creusot-contracts/src/std/iter/skip.rs" 76 4 76 10
+  let%span sskip4 = "../../../creusot-contracts/src/std/iter/skip.rs" 62 12 67 74
+  let%span sskip5 = "../../../creusot-contracts/src/std/iter/skip.rs" 21 14 21 50
+  let%span sskip6 = "../../../creusot-contracts/src/std/iter/skip.rs" 14 14 14 39
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
+  
+  type t_I'0
+  
+  use prelude.prelude.UIntSize
+  
+  type t_Skip'0  =
+    { t_Skip__iter'0: t_I'0; t_Skip__n'0: usize }
+  
+  type t_Item'0
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use prelude.prelude.Int
+  
+  constant v_MAX'0 : usize = (18446744073709551615 : usize)
+  
+  use prelude.prelude.UIntSize
+  
+  function n'0 [#"../../../creusot-contracts/src/std/iter/skip.rs" 22 4 22 21] (self : t_Skip'0) : int
   
   axiom n'0_spec : forall self : t_Skip'0 . [%#sskip5] n'0 self >= 0 /\ n'0 self <= UIntSize.to_int (v_MAX'0 : usize)
   
@@ -8038,16 +8724,16 @@ module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produ
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter8] produces'1 a ab b)
    -> ([%#siter9] produces'1 b bc c)  -> ([%#siter10] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter7] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -8089,10 +8775,10 @@ module M_creusot_contracts__stdqy35z1__iter__take__qyi12344256497067751022__prod
   let%span stake2 = "../../../creusot-contracts/src/std/iter/take.rs" 65 12 65 88
   let%span stake3 = "../../../creusot-contracts/src/std/iter/take.rs" 31 14 31 50
   let%span stake4 = "../../../creusot-contracts/src/std/iter/take.rs" 17 14 17 39
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -8134,16 +8820,16 @@ module M_creusot_contracts__stdqy35z1__iter__take__qyi12344256497067751022__prod
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter6] produces'1 a ab b)
    -> ([%#siter7] produces'1 b bc c)  -> ([%#siter8] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter5] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -8166,10 +8852,10 @@ module M_creusot_contracts__stdqy35z1__iter__take__qyi12344256497067751022__prod
   let%span stake4 = "../../../creusot-contracts/src/std/iter/take.rs" 65 12 65 88
   let%span stake5 = "../../../creusot-contracts/src/std/iter/take.rs" 31 14 31 50
   let%span stake6 = "../../../creusot-contracts/src/std/iter/take.rs" 17 14 17 39
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -8211,16 +8897,16 @@ module M_creusot_contracts__stdqy35z1__iter__take__qyi12344256497067751022__prod
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter8] produces'1 a ab b)
    -> ([%#siter9] produces'1 b bc c)  -> ([%#siter10] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter7] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -8251,10 +8937,10 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   let%span szip2 = "../../../creusot-contracts/src/std/iter/zip.rs" 46 12 49 95
   let%span szip3 = "../../../creusot-contracts/src/std/iter/zip.rs" 14 14 14 39
   let%span szip4 = "../../../creusot-contracts/src/std/iter/zip.rs" 21 14 21 39
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -8311,16 +8997,16 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_A'0) (visited : Seq.seq t_Item'0) (o : t_A'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_A'0) (visited : Seq.seq t_Item'0) (o : t_A'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_A'0) (ab : Seq.seq t_Item'0) (b : t_A'0) (bc : Seq.seq t_Item'0) (c : t_A'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_A'0) (ab : Seq.seq t_Item'0) (b : t_A'0) (bc : Seq.seq t_Item'0) (c : t_A'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_A'0, ab : Seq.seq t_Item'0, b : t_A'0, bc : Seq.seq t_Item'0, c : t_A'0 . ([%#siter6] produces'1 a ab b)
    -> ([%#siter7] produces'1 b bc c)  -> ([%#siter8] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_A'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_A'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_A'0 . [%#siter5] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -8332,16 +9018,16 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   
   use seq.Seq
   
-  predicate produces'2 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_B'0) (visited : Seq.seq t_Item'1) (o : t_B'0)
+  predicate produces'2 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_B'0) (visited : Seq.seq t_Item'1) (o : t_B'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_B'0) (ab : Seq.seq t_Item'1) (b : t_B'0) (bc : Seq.seq t_Item'1) (c : t_B'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_B'0) (ab : Seq.seq t_Item'1) (b : t_B'0) (bc : Seq.seq t_Item'1) (c : t_B'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_B'0, ab : Seq.seq t_Item'1, b : t_B'0, bc : Seq.seq t_Item'1, c : t_B'0 . ([%#siter6] produces'2 a ab b)
    -> ([%#siter7] produces'2 b bc c)  -> ([%#siter8] produces'2 a (Seq.(++) ab bc) c)
   
-  function produces_refl'2 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_B'0) : ()
+  function produces_refl'2 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_B'0) : ()
   
   axiom produces_refl'2_spec : forall self : t_B'0 . [%#siter5] produces'2 self (Seq.empty  : Seq.seq t_Item'1) self
   
@@ -8367,10 +9053,10 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   let%span szip4 = "../../../creusot-contracts/src/std/iter/zip.rs" 46 12 49 95
   let%span szip5 = "../../../creusot-contracts/src/std/iter/zip.rs" 14 14 14 39
   let%span szip6 = "../../../creusot-contracts/src/std/iter/zip.rs" 21 14 21 39
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_A'0
   
@@ -8425,16 +9111,16 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_A'0) (visited : Seq.seq t_Item'0) (o : t_A'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_A'0) (visited : Seq.seq t_Item'0) (o : t_A'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_A'0) (ab : Seq.seq t_Item'0) (b : t_A'0) (bc : Seq.seq t_Item'0) (c : t_A'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_A'0) (ab : Seq.seq t_Item'0) (b : t_A'0) (bc : Seq.seq t_Item'0) (c : t_A'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_A'0, ab : Seq.seq t_Item'0, b : t_A'0, bc : Seq.seq t_Item'0, c : t_A'0 . ([%#siter8] produces'1 a ab b)
    -> ([%#siter9] produces'1 b bc c)  -> ([%#siter10] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_A'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_A'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_A'0 . [%#siter7] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -8446,16 +9132,16 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   
   use seq.Seq
   
-  predicate produces'2 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_B'0) (visited : Seq.seq t_Item'1) (o : t_B'0)
+  predicate produces'2 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_B'0) (visited : Seq.seq t_Item'1) (o : t_B'0)
     
   
-  function produces_trans'2 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_B'0) (ab : Seq.seq t_Item'1) (b : t_B'0) (bc : Seq.seq t_Item'1) (c : t_B'0) : ()
+  function produces_trans'2 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_B'0) (ab : Seq.seq t_Item'1) (b : t_B'0) (bc : Seq.seq t_Item'1) (c : t_B'0) : ()
     
   
   axiom produces_trans'2_spec : forall a : t_B'0, ab : Seq.seq t_Item'1, b : t_B'0, bc : Seq.seq t_Item'1, c : t_B'0 . ([%#siter8] produces'2 a ab b)
    -> ([%#siter9] produces'2 b bc c)  -> ([%#siter10] produces'2 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_B'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_B'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_B'0 . [%#siter7] produces'2 self (Seq.empty  : Seq.seq t_Item'1) self
   
@@ -8485,14 +9171,14 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   goal vc_produces_trans'0 : ([%#szip1] produces'0 b bc c)
    -> ([%#szip0] produces'0 a ab b)  -> ([%#szip2] produces'0 a (Seq.(++) ab bc) c)
 end
-module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_refl [#"../../../creusot-contracts/src/std/iter.rs" 223 4 223 26] (* <&mut I as std::iter::Iterator> *)
-  let%span siter0 = "../../../creusot-contracts/src/std/iter.rs" 222 14 222 45
-  let%span siter1 = "../../../creusot-contracts/src/std/iter.rs" 220 4 220 10
-  let%span siter2 = "../../../creusot-contracts/src/std/iter.rs" 211 20 211 64
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_refl [#"../../../creusot-contracts/src/std/iter.rs" 279 4 279 26] (* <&mut I as std::iter::Iterator> *)
+  let%span siter0 = "../../../creusot-contracts/src/std/iter.rs" 278 14 278 45
+  let%span siter1 = "../../../creusot-contracts/src/std/iter.rs" 276 4 276 10
+  let%span siter2 = "../../../creusot-contracts/src/std/iter.rs" 267 20 267 64
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use seq.Seq
   
@@ -8506,40 +9192,40 @@ module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_re
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter4] produces'1 a ab b)
    -> ([%#siter5] produces'1 b bc c)  -> ([%#siter6] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter3] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 210 4 210 64] (self : borrowed t_I'0) (visited : Seq.seq t_Item'0) (o : borrowed t_I'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 266 4 266 64] (self : borrowed t_I'0) (visited : Seq.seq t_Item'0) (o : borrowed t_I'0)
     
    =
     [%#siter2] produces'1 self.current visited o.current /\ self.final = o.final
   
   constant self  : borrowed t_I'0
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 223 4 223 26] (self : borrowed t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 279 4 279 26] (self : borrowed t_I'0) : ()
   
   goal vc_produces_refl'0 : [%#siter0] produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
 end
-module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_trans [#"../../../creusot-contracts/src/std/iter.rs" 230 4 230 90] (* <&mut I as std::iter::Iterator> *)
-  let%span siter0 = "../../../creusot-contracts/src/std/iter.rs" 227 15 227 32
-  let%span siter1 = "../../../creusot-contracts/src/std/iter.rs" 228 15 228 32
-  let%span siter2 = "../../../creusot-contracts/src/std/iter.rs" 229 14 229 42
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 225 4 225 10
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 211 20 211 64
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_trans [#"../../../creusot-contracts/src/std/iter.rs" 286 4 286 90] (* <&mut I as std::iter::Iterator> *)
+  let%span siter0 = "../../../creusot-contracts/src/std/iter.rs" 283 15 283 32
+  let%span siter1 = "../../../creusot-contracts/src/std/iter.rs" 284 15 284 32
+  let%span siter2 = "../../../creusot-contracts/src/std/iter.rs" 285 14 285 42
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 281 4 281 10
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 267 20 267 64
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter8 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use prelude.prelude.Borrow
   
@@ -8553,20 +9239,20 @@ module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_tr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter6] produces'1 a ab b)
    -> ([%#siter7] produces'1 b bc c)  -> ([%#siter8] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter5] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 210 4 210 64] (self : borrowed t_I'0) (visited : Seq.seq t_Item'0) (o : borrowed t_I'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 266 4 266 64] (self : borrowed t_I'0) (visited : Seq.seq t_Item'0) (o : borrowed t_I'0)
     
    =
     [%#siter4] produces'1 self.current visited o.current /\ self.final = o.final
@@ -8581,7 +9267,7 @@ module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_tr
   
   constant c  : borrowed t_I'0
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 230 4 230 90] (a : borrowed t_I'0) (ab : Seq.seq t_Item'0) (b : borrowed t_I'0) (bc : Seq.seq t_Item'0) (c : borrowed t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 286 4 286 90] (a : borrowed t_I'0) (ab : Seq.seq t_Item'0) (b : borrowed t_I'0) (bc : Seq.seq t_Item'0) (c : borrowed t_I'0) : ()
     
   
   goal vc_produces_trans'0 : ([%#siter1] produces'0 b bc c)
@@ -12819,30 +13505,1031 @@ module M_creusot_contracts__logic__fmap__qyi9892930999379617882__contains_ghost
       (! return' {result}) ]
     
   
-  predicate invariant'2 [#"../../../creusot-contracts/src/invariant.rs" 23 4 23 30] (self : t_Option'0) =
-    [%#sinvariant13] inv'2 self
+  predicate invariant'2 [#"../../../creusot-contracts/src/invariant.rs" 23 4 23 30] (self : t_Option'0) =
+    [%#sinvariant13] inv'2 self
+  
+  predicate inv'3 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Option'0)
+  
+  axiom inv_axiom'3 [@rewrite] : forall x : t_Option'0 [inv'3 x] . inv'3 x = invariant'2 x
+  
+  let rec is_some'0 (self:t_Option'0) (return'  (ret:bool))= {[@expl:is_some 'self' type invariant] inv'3 self}
+    any [ return' (result:bool)-> {[%#soption7] result = (self <> C_None'0)} (! return' {result}) ] 
+  
+  use prelude.prelude.Intrinsic
+  
+  meta "compute_max_steps" 1000000
+  
+  let rec contains_ghost'0 (self:t_FMap'0) (key:t_K'0) (return'  (ret:bool))= {[@expl:contains_ghost 'self' type invariant] [%#sfmap0] inv'0 self}
+    {[@expl:contains_ghost 'key' type invariant] [%#sfmap1] inv'1 key}
+    (! bb0
+    [ bb0 = s0 [ s0 = get_ghost'0 {self} {key} (fun (_ret':t_Option'0) ->  [ &_5 <- _ret' ] s1) | s1 = bb1 ] 
+    | bb1 = s0 [ s0 = is_some'0 {_5} (fun (_ret':bool) ->  [ &_0 <- _ret' ] s1) | s1 = bb2 ] 
+    | bb2 = return' {_0} ]
+    ) [ & _0 : bool = any_l () | & self : t_FMap'0 = self | & key : t_K'0 = key | & _5 : t_Option'0 = any_l () ] 
+    [ return' (result:bool)-> {[@expl:contains_ghost ensures] [%#sfmap2] result = contains'0 self key}
+      (! return' {result}) ]
+    
+end
+module M_creusot_contracts__logic__fset__qyi12147533290214288165__ext_eq [#"../../../creusot-contracts/src/logic/fset.rs" 186 4 188 17] (* logic::fset::FSet<T> *)
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 185 14 185 38
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 191 12 191 63
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  
+  type t_T'0
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_T'0) (e : t_T'0)
+    
+   =
+    [%#sfset2] Fset.mem e self
+  
+  constant self  : Fset.fset t_T'0
+  
+  constant other  : Fset.fset t_T'0
+  
+  predicate ext_eq'0 [#"../../../creusot-contracts/src/logic/fset.rs" 186 4 188 17] (self : Fset.fset t_T'0) (other : Fset.fset t_T'0)
+    
+  
+  goal vc_ext_eq'0 : [%#sfset0] ([%#sfset1] forall e : t_T'0 . contains'0 self e = contains'0 other e)  -> self = other
+end
+module M_creusot_contracts__logic__fset__qyi12147533290214288165__singleton [#"../../../creusot-contracts/src/logic/fset.rs" 201 4 201 34] (* logic::fset::FSet<T> *)
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 200 14 200 57
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 202 8 202 29
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 65 8 65 26
+  
+  type t_T'0
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_T'0) (e : t_T'0)
+    
+   =
+    [%#sfset2] Fset.mem e self
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function insert'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 64 4 64 37] (self : Fset.fset t_T'0) (e : t_T'0) : Fset.fset t_T'0
+    
+   =
+    [%#sfset3] Fset.add e self
+  
+  constant x  : t_T'0
+  
+  function singleton'0 [#"../../../creusot-contracts/src/logic/fset.rs" 201 4 201 34] (x : t_T'0) : Fset.fset t_T'0
+  
+  goal vc_singleton'0 : [%#sfset0] forall y : t_T'0 . contains'0 (insert'0 (Fset.empty : Fset.fset t_T'0) x) y = (x = y)
+end
+module M_creusot_contracts__logic__fset__qyi12147533290214288165__unions [#"../../../creusot-contracts/src/logic/fset.rs" 210 4 210 61] (* logic::fset::FSet<T> *)
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 208 14 208 102
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 209 14 209 24
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 206 4 206 12
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 92 8 92 26
+  
+  type t_U'0
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_U'0) (e : t_U'0)
+    
+   =
+    [%#sfset3] Fset.mem e self
+  
+  type t_T'0
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'1 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_T'0) (e : t_T'0)
+    
+   =
+    [%#sfset3] Fset.mem e self
+  
+  use map.Map
+  
+  use set.Fset
+  
+  use map.Map
+  
+  use prelude.prelude.Int
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function remove'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 91 4 91 37] (self : Fset.fset t_T'0) (e : t_T'0) : Fset.fset t_T'0
+    
+   =
+    [%#sfset4] Fset.remove e self
+  
+  use set.Fset
+  
+  constant self  : Fset.fset t_T'0
+  
+  constant f  : Map.map t_T'0 (Fset.fset t_U'0)
+  
+  function unions'0 [#"../../../creusot-contracts/src/logic/fset.rs" 210 4 210 61] (self : Fset.fset t_T'0) (f : Map.map t_T'0 (Fset.fset t_U'0)) : Fset.fset t_U'0
+    
+  
+  goal vc_unions'0 : if Fset.cardinal self = 0 then
+    [%#sfset0] forall y : t_U'0 . contains'0 (Fset.empty : Fset.fset t_U'0) y
+    = (exists x : t_T'0 . contains'1 self x /\ contains'0 (Map.get f x) y)
+  else
+    let x = Fset.pick self in (0 <= ([%#sfset1] Fset.cardinal self)
+    /\ ([%#sfset1] Fset.cardinal (remove'0 self x)) < ([%#sfset1] Fset.cardinal self))
+    /\ (([%#sfset0] forall y : t_U'0 . contains'0 (unions'0 (remove'0 self x) f) y
+    = (exists x' : t_T'0 . contains'1 (remove'0 self x) x' /\ contains'0 (Map.get f x') y))
+     -> ([%#sfset0] forall y : t_U'0 . contains'0 (Fset.union (Map.get f x) (unions'0 (remove'0 self x) f)) y
+    = (exists x : t_T'0 . contains'1 self x /\ contains'0 (Map.get f x) y)))
+  
+end
+module M_creusot_contracts__logic__fset__qyi12147533290214288165__replicate [#"../../../creusot-contracts/src/logic/fset.rs" 267 4 267 50] (* logic::fset::FSet<T> *)
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 264 15 264 21
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 265 14 265 123
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 266 14 266 15
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 270 32 270 85
+  let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 200 14 200 57
+  let%span sfset5 = "../../../creusot-contracts/src/logic/fset.rs" 273 32 273 108
+  let%span sfset6 = "../../../creusot-contracts/src/logic/fset.rs" 247 14 247 117
+  let%span sfset7 = "../../../creusot-contracts/src/logic/fset.rs" 268 8 276 9
+  let%span sfset8 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  let%span sseq9 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
+  let%span sfset10 = "../../../creusot-contracts/src/logic/fset.rs" 202 8 202 29
+  let%span sseq11 = "../../../creusot-contracts/src/logic/seq.rs" 173 8 173 39
+  let%span sfset12 = "../../../creusot-contracts/src/logic/fset.rs" 65 8 65 26
+  
+  use prelude.prelude.Int
+  
+  type t_T'0
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0)
+    
+   =
+    [%#sfset8] Fset.mem e self
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate contains'1 [#"../../../creusot-contracts/src/logic/seq.rs" 351 4 353 17] (self : Seq.seq t_T'0) (x : t_T'0)
+   =
+    [%#sseq9] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'2 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_T'0) (e : t_T'0)
+    
+   =
+    [%#sfset8] Fset.mem e self
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function insert'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 64 4 64 37] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset12] Fset.add e self
+  
+  function singleton'0 [#"../../../creusot-contracts/src/logic/fset.rs" 201 4 201 34] (x : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset10] insert'0 (Fset.empty  : Fset.fset (Seq.seq t_T'0)) x
+  
+  axiom singleton'0_spec : forall x : Seq.seq t_T'0 . [%#sfset4] forall y : Seq.seq t_T'0 . contains'0 (singleton'0 x) y
+  = (x = y)
+  
+  use seq.Seq
+  
+  function tail'0 [#"../../../creusot-contracts/src/logic/seq.rs" 172 4 172 29] (self : Seq.seq t_T'0) : Seq.seq t_T'0 =
+    [%#sseq11] Seq.([..]) self 1 (Seq.length self)
+  
+  function cons'0 [#"../../../creusot-contracts/src/logic/fset.rs" 248 4 248 61] (s : Fset.fset t_T'0) (ss : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom cons'0_spec : forall s : Fset.fset t_T'0, ss : Fset.fset (Seq.seq t_T'0) . [%#sfset6] forall xs : Seq.seq t_T'0 . contains'0 (cons'0 s ss) xs
+  = (0 < Seq.length xs /\ contains'2 s (Seq.get xs 0) /\ contains'0 ss (tail'0 xs))
+  
+  constant self  : Fset.fset t_T'0
+  
+  constant n  : int
+  
+  function replicate'0 [#"../../../creusot-contracts/src/logic/fset.rs" 267 4 267 50] (self : Fset.fset t_T'0) (n : int) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  goal vc_replicate'0 : ([%#sfset0] n >= 0)
+   -> (if n = 0 then
+    ([%#sfset3] forall xs : Seq.seq t_T'0 . Seq.length xs = 0  -> xs = (Seq.empty  : Seq.seq t_T'0))
+    && (let _ = () in let _ = () in ([%#sfset4] forall y : Seq.seq t_T'0 . contains'0 (singleton'0 (Seq.empty : Seq.seq t_T'0)) y
+    = ((Seq.empty : Seq.seq t_T'0) = y))
+     -> ([%#sfset1] forall xs : Seq.seq t_T'0 . contains'0 (singleton'0 (Seq.empty : Seq.seq t_T'0)) xs
+    = (Seq.length xs = n /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x))))
+  else
+    ([%#sfset5] forall xs : Seq.seq t_T'0, i : int . 0 < i /\ i < Seq.length xs
+     -> Seq.get xs i = Seq.get (tail'0 xs) (i - 1))
+    && (let _ = () in let _ = () in (([@expl:replicate requires] [%#sfset0] n - 1 >= 0)
+    /\ 0 <= ([%#sfset2] n) /\ ([%#sfset2] n - 1) < ([%#sfset2] n))
+    /\ (([%#sfset1] forall xs : Seq.seq t_T'0 . contains'0 (replicate'0 self (n - 1)) xs
+    = (Seq.length xs = n - 1 /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x)))
+     -> ([%#sfset6] forall xs : Seq.seq t_T'0 . contains'0 (cons'0 self (replicate'0 self (n - 1))) xs
+    = (0 < Seq.length xs /\ contains'2 self (Seq.get xs 0) /\ contains'0 (replicate'0 self (n - 1)) (tail'0 xs)))
+     -> ([%#sfset1] forall xs : Seq.seq t_T'0 . contains'0 (cons'0 self (replicate'0 self (n - 1))) xs
+    = (Seq.length xs = n /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x)))))
+  )
+end
+module M_creusot_contracts__logic__fset__qyi12147533290214288165__replicate_up_to [#"../../../creusot-contracts/src/logic/fset.rs" 285 4 285 56] (* logic::fset::FSet<T> *)
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 282 15 282 21
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 283 14 283 123
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 284 14 284 15
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 288 32 288 85
+  let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 200 14 200 57
+  let%span sfset5 = "../../../creusot-contracts/src/logic/fset.rs" 264 15 264 21
+  let%span sfset6 = "../../../creusot-contracts/src/logic/fset.rs" 265 14 265 123
+  let%span sfset7 = "../../../creusot-contracts/src/logic/fset.rs" 266 14 266 15
+  let%span sfset8 = "../../../creusot-contracts/src/logic/fset.rs" 286 8 293 9
+  let%span sfset9 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  let%span sseq10 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
+  let%span sfset11 = "../../../creusot-contracts/src/logic/fset.rs" 202 8 202 29
+  let%span sfset12 = "../../../creusot-contracts/src/logic/fset.rs" 268 8 276 9
+  let%span sfset13 = "../../../creusot-contracts/src/logic/fset.rs" 65 8 65 26
+  let%span sfset14 = "../../../creusot-contracts/src/logic/fset.rs" 247 14 247 117
+  let%span sseq15 = "../../../creusot-contracts/src/logic/seq.rs" 173 8 173 39
+  
+  use prelude.prelude.Int
+  
+  type t_T'0
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0)
+    
+   =
+    [%#sfset9] Fset.mem e self
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate contains'1 [#"../../../creusot-contracts/src/logic/seq.rs" 351 4 353 17] (self : Seq.seq t_T'0) (x : t_T'0)
+   =
+    [%#sseq10] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'2 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_T'0) (e : t_T'0)
+    
+   =
+    [%#sfset9] Fset.mem e self
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function insert'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 64 4 64 37] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset13] Fset.add e self
+  
+  function singleton'0 [#"../../../creusot-contracts/src/logic/fset.rs" 201 4 201 34] (x : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset11] insert'0 (Fset.empty  : Fset.fset (Seq.seq t_T'0)) x
+  
+  axiom singleton'0_spec : forall x : Seq.seq t_T'0 . [%#sfset4] forall y : Seq.seq t_T'0 . contains'0 (singleton'0 x) y
+  = (x = y)
+  
+  use seq.Seq
+  
+  function tail'0 [#"../../../creusot-contracts/src/logic/seq.rs" 172 4 172 29] (self : Seq.seq t_T'0) : Seq.seq t_T'0 =
+    [%#sseq15] Seq.([..]) self 1 (Seq.length self)
+  
+  function cons'0 [#"../../../creusot-contracts/src/logic/fset.rs" 248 4 248 61] (s : Fset.fset t_T'0) (ss : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom cons'0_spec : forall s : Fset.fset t_T'0, ss : Fset.fset (Seq.seq t_T'0) . [%#sfset14] forall xs : Seq.seq t_T'0 . contains'0 (cons'0 s ss) xs
+  = (0 < Seq.length xs /\ contains'2 s (Seq.get xs 0) /\ contains'0 ss (tail'0 xs))
+  
+  function replicate'0 [#"../../../creusot-contracts/src/logic/fset.rs" 267 4 267 50] (self : Fset.fset t_T'0) (n : int) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom replicate'0_def : forall self : Fset.fset t_T'0, n : int . ([%#sfset5] n >= 0)
+   -> replicate'0 self n
+  = ([%#sfset12] if n = 0 then
+    let _ = let _ = () in () in singleton'0 (Seq.empty  : Seq.seq t_T'0)
+  else
+    let _ = let _ = () in () in cons'0 self (replicate'0 self (n - 1))
+  )
+  
+  axiom replicate'0_spec : forall self : Fset.fset t_T'0, n : int . ([%#sfset5] n >= 0)
+   -> ([%#sfset6] forall xs : Seq.seq t_T'0 . contains'0 (replicate'0 self n) xs
+  = (Seq.length xs = n /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x)))
+  
+  use set.Fset
+  
+  constant self  : Fset.fset t_T'0
+  
+  constant n  : int
+  
+  function replicate_up_to'0 [#"../../../creusot-contracts/src/logic/fset.rs" 285 4 285 56] (self : Fset.fset t_T'0) (n : int) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  goal vc_replicate_up_to'0 : ([%#sfset0] n >= 0)
+   -> (if n = 0 then
+    ([%#sfset3] forall xs : Seq.seq t_T'0 . Seq.length xs = 0  -> xs = (Seq.empty  : Seq.seq t_T'0))
+    && (let _ = () in let _ = () in ([%#sfset4] forall y : Seq.seq t_T'0 . contains'0 (singleton'0 (Seq.empty : Seq.seq t_T'0)) y
+    = ((Seq.empty : Seq.seq t_T'0) = y))
+     -> ([%#sfset1] forall xs : Seq.seq t_T'0 . contains'0 (singleton'0 (Seq.empty : Seq.seq t_T'0)) xs
+    = (Seq.length xs <= n /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x))))
+  else
+    (([@expl:replicate_up_to requires] [%#sfset0] n - 1 >= 0)
+    /\ 0 <= ([%#sfset2] n) /\ ([%#sfset2] n - 1) < ([%#sfset2] n))
+    /\ (([%#sfset1] forall xs : Seq.seq t_T'0 . contains'0 (replicate_up_to'0 self (n - 1)) xs
+    = (Seq.length xs <= n - 1 /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x)))
+     -> ([@expl:replicate requires] [%#sfset5] n >= 0)
+    /\ (([%#sfset6] forall xs : Seq.seq t_T'0 . contains'0 (replicate'0 self n) xs
+    = (Seq.length xs = n /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x)))
+     -> ([%#sfset1] forall xs : Seq.seq t_T'0 . contains'0 (Fset.union (replicate_up_to'0 self (n
+    - 1)) (replicate'0 self n)) xs
+    = (Seq.length xs <= n /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x)))))
+  )
+end
+module M_creusot_contracts__logic__fset__unions_union [#"../../../creusot-contracts/src/logic/fset.rs" 469 0 469 27]
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 466 10 466 125
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 467 10 468 76
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 464 0 464 8
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 208 14 208 102
+  let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 209 14 209 24
+  let%span sfset5 = "../../../creusot-contracts/src/logic/fset.rs" 206 4 206 12
+  let%span sfset6 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  let%span sfset7 = "../../../creusot-contracts/src/logic/fset.rs" 92 8 92 26
+  
+  type t_T'0
+  
+  use set.Fset
+  
+  type t_U'0
+  
+  use set.Fset
+  
+  use map.Map
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_U'0) (e : t_U'0)
+    
+   =
+    [%#sfset6] Fset.mem e self
+  
+  use set.Fset
+  
+  predicate contains'1 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_T'0) (e : t_T'0)
+    
+   =
+    [%#sfset6] Fset.mem e self
+  
+  use map.Map
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function remove'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 91 4 91 37] (self : Fset.fset t_T'0) (e : t_T'0) : Fset.fset t_T'0
+    
+   =
+    [%#sfset7] Fset.remove e self
+  
+  use set.Fset
+  
+  function unions'0 [#"../../../creusot-contracts/src/logic/fset.rs" 210 4 210 61] (self : Fset.fset t_T'0) (f : Map.map t_T'0 (Fset.fset t_U'0)) : Fset.fset t_U'0
+    
+  
+  axiom unions'0_def : forall self : Fset.fset t_T'0, f : Map.map t_T'0 (Fset.fset t_U'0) . unions'0 self f
+  = ([%#sfset5] if Fset.cardinal self = 0 then
+    Fset.empty  : Fset.fset t_U'0
+  else
+    let x = Fset.pick self in Fset.union (Map.get f x) (unions'0 (remove'0 self x) f)
+  )
+  
+  axiom unions'0_spec : forall self : Fset.fset t_T'0, f : Map.map t_T'0 (Fset.fset t_U'0) . [%#sfset3] forall y : t_U'0 . contains'0 (unions'0 self f) y
+  = (exists x : t_T'0 . contains'1 self x /\ contains'0 (Map.get f x) y)
+  
+  use prelude.prelude.Mapping
+  
+  constant _1  : ()
+  
+  function unions_union'0 [#"../../../creusot-contracts/src/logic/fset.rs" 469 0 469 27] (_1 : ()) : ()
+  
+  goal vc_unions_union'0 : ([%#sfset0] forall s1 : Fset.fset t_T'0, s2 : Fset.fset t_T'0, f : Map.map t_T'0 (Fset.fset t_U'0) . unions'0 (Fset.union s1 s2) f
+  = Fset.union (unions'0 s1 f) (unions'0 s2 f))
+  && ([%#sfset1] forall s : Fset.fset t_T'0, f : Map.map t_T'0 (Fset.fset t_U'0), g : Map.map t_T'0 (Fset.fset t_U'0) . unions'0 s (Mapping.from_fn (fun (x : t_T'0) -> Fset.union (Map.get f x) (Map.get g x)))
+  = Fset.union (unions'0 s f) (unions'0 s g))
+end
+module M_creusot_contracts__logic__fset__map_union [#"../../../creusot-contracts/src/logic/fset.rs" 475 0 475 24]
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 474 10 474 104
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 472 0 472 8
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 231 8 231 27
+  
+  type t_T'0
+  
+  use set.Fset
+  
+  type t_U'0
+  
+  use map.Map
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function map'0 [#"../../../creusot-contracts/src/logic/fset.rs" 230 4 230 52] (self : Fset.fset t_T'0) (f : Map.map t_T'0 t_U'0) : Fset.fset t_U'0
+    
+   =
+    [%#sfset2] Fset.map f self
+  
+  use set.Fset
+  
+  constant _1  : ()
+  
+  function map_union'0 [#"../../../creusot-contracts/src/logic/fset.rs" 475 0 475 24] (_1 : ()) : ()
+  
+  goal vc_map_union'0 : [%#sfset0] forall s : Fset.fset t_T'0, t : Fset.fset t_T'0, f : Map.map t_T'0 t_U'0 . map'0 (Fset.union s t) f
+  = Fset.union (map'0 s f) (map'0 t f)
+end
+module M_creusot_contracts__logic__fset__concat_union [#"../../../creusot-contracts/src/logic/fset.rs" 484 0 484 24]
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 480 10 481 83
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 482 10 483 83
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 478 0 478 8
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 256 14 256 144
+  let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  
+  type t_T'0
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0)
+    
+   =
+    [%#sfset4] Fset.mem e self
+  
+  use seq.Seq
+  
+  function concat'0 [#"../../../creusot-contracts/src/logic/fset.rs" 257 4 257 67] (s : Fset.fset (Seq.seq t_T'0)) (t : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom concat'0_spec : forall s : Fset.fset (Seq.seq t_T'0), t : Fset.fset (Seq.seq t_T'0) . [%#sfset3] forall xs : Seq.seq t_T'0 . contains'0 (concat'0 s t) xs
+  = (exists ys : Seq.seq t_T'0, zs : Seq.seq t_T'0 . contains'0 s ys /\ contains'0 t zs /\ xs = Seq.(++) ys zs)
+  
+  constant _1  : ()
+  
+  function concat_union'0 [#"../../../creusot-contracts/src/logic/fset.rs" 484 0 484 24] (_1 : ()) : ()
+  
+  goal vc_concat_union'0 : ([%#sfset0] forall s1 : Fset.fset (Seq.seq t_T'0), s2 : Fset.fset (Seq.seq t_T'0), t : Fset.fset (Seq.seq t_T'0) . concat'0 (Fset.union s1 s2) t
+  = Fset.union (concat'0 s1 t) (concat'0 s2 t))
+  && ([%#sfset1] forall s : Fset.fset (Seq.seq t_T'0), t1 : Fset.fset (Seq.seq t_T'0), t2 : Fset.fset (Seq.seq t_T'0) . concat'0 s (Fset.union t1 t2)
+  = Fset.union (concat'0 s t1) (concat'0 s t2))
+end
+module M_creusot_contracts__logic__fset__cons_concat [#"../../../creusot-contracts/src/logic/fset.rs" 490 0 490 23]
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 489 10 489 133
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 491 20 491 115
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 492 20 492 74
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 493 20 493 89
+  let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 491 4 491 117
+  let%span sfset5 = "../../../creusot-contracts/src/logic/fset.rs" 247 14 247 117
+  let%span sfset6 = "../../../creusot-contracts/src/logic/fset.rs" 256 14 256 144
+  let%span sseq7 = "../../../creusot-contracts/src/logic/seq.rs" 251 8 251 27
+  let%span sseq8 = "../../../creusot-contracts/src/logic/seq.rs" 173 8 173 39
+  let%span sfset9 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  
+  type t_T'0
+  
+  use set.Fset
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0)
+    
+   =
+    [%#sfset9] Fset.mem e self
+  
+  use seq.Seq
+  
+  use prelude.prelude.Int
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  predicate contains'1 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_T'0) (e : t_T'0)
+    
+   =
+    [%#sfset9] Fset.mem e self
+  
+  use seq.Seq
+  
+  function tail'0 [#"../../../creusot-contracts/src/logic/seq.rs" 172 4 172 29] (self : Seq.seq t_T'0) : Seq.seq t_T'0 =
+    [%#sseq8] Seq.([..]) self 1 (Seq.length self)
+  
+  function cons'0 [#"../../../creusot-contracts/src/logic/fset.rs" 248 4 248 61] (s : Fset.fset t_T'0) (ss : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom cons'0_spec : forall s : Fset.fset t_T'0, ss : Fset.fset (Seq.seq t_T'0) . [%#sfset5] forall xs : Seq.seq t_T'0 . contains'0 (cons'0 s ss) xs
+  = (0 < Seq.length xs /\ contains'1 s (Seq.get xs 0) /\ contains'0 ss (tail'0 xs))
+  
+  use seq.Seq
+  
+  function concat'0 [#"../../../creusot-contracts/src/logic/fset.rs" 257 4 257 67] (s : Fset.fset (Seq.seq t_T'0)) (t : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom concat'0_spec : forall s : Fset.fset (Seq.seq t_T'0), t : Fset.fset (Seq.seq t_T'0) . [%#sfset6] forall xs : Seq.seq t_T'0 . contains'0 (concat'0 s t) xs
+  = (exists ys : Seq.seq t_T'0, zs : Seq.seq t_T'0 . contains'0 s ys /\ contains'0 t zs /\ xs = Seq.(++) ys zs)
+  
+  use seq.Seq
+  
+  function push_front'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/seq.rs" 250 4 250 41] (self : Seq.seq t_T'0) (x : t_T'0) : Seq.seq t_T'0
+    
+   =
+    [%#sseq7] Seq.cons x self
+  
+  constant _1  : ()
+  
+  function cons_concat'0 [#"../../../creusot-contracts/src/logic/fset.rs" 490 0 490 23] (_1 : ()) : ()
+  
+  goal vc_cons_concat'0 : ([%#sfset1] forall x : t_T'0, xs : Seq.seq t_T'0, ys : Seq.seq t_T'0 . Seq.(++) (push_front'0 xs x) ys
+  = push_front'0 (Seq.(++) xs ys) x)
+  && (let _ = () in let _ = () in ([%#sfset2] forall x : t_T'0, ys : Seq.seq t_T'0 . tail'0 (push_front'0 ys x) = ys)
+  && (let _ = () in let _ = () in ([%#sfset3] forall ys : Seq.seq t_T'0 . 0 < Seq.length ys
+   -> ys = push_front'0 (tail'0 ys) (Seq.get ys 0))
+  && (let _ = () in let _ = () in [%#sfset0] forall s : Fset.fset t_T'0, t : Fset.fset (Seq.seq t_T'0), u : Fset.fset (Seq.seq t_T'0) . concat'0 (cons'0 s t) u
+  = cons'0 s (concat'0 t u))))
+end
+module M_creusot_contracts__logic__fset__concat_replicate [#"../../../creusot-contracts/src/logic/fset.rs" 502 0 502 54]
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 499 11 499 27
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 500 10 500 76
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 501 10 501 11
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 264 15 264 21
+  let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 265 14 265 123
+  let%span sfset5 = "../../../creusot-contracts/src/logic/fset.rs" 266 14 266 15
+  let%span sfset6 = "../../../creusot-contracts/src/logic/fset.rs" 516 10 516 59
+  let%span sfset7 = "../../../creusot-contracts/src/logic/fset.rs" 517 10 517 59
+  let%span sfset8 = "../../../creusot-contracts/src/logic/fset.rs" 489 10 489 133
+  let%span sfset9 = "../../../creusot-contracts/src/logic/fset.rs" 503 4 510 5
+  let%span sfset10 = "../../../creusot-contracts/src/logic/fset.rs" 268 8 276 9
+  let%span sfset11 = "../../../creusot-contracts/src/logic/fset.rs" 256 14 256 144
+  let%span sfset12 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  let%span sseq13 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
+  let%span sfset14 = "../../../creusot-contracts/src/logic/fset.rs" 519 4 519 68
+  let%span sfset15 = "../../../creusot-contracts/src/logic/fset.rs" 200 14 200 57
+  let%span sfset16 = "../../../creusot-contracts/src/logic/fset.rs" 202 8 202 29
+  let%span sfset17 = "../../../creusot-contracts/src/logic/fset.rs" 491 4 491 117
+  let%span sfset18 = "../../../creusot-contracts/src/logic/fset.rs" 247 14 247 117
+  let%span sfset19 = "../../../creusot-contracts/src/logic/fset.rs" 65 8 65 26
+  let%span sseq20 = "../../../creusot-contracts/src/logic/seq.rs" 173 8 173 39
+  
+  use prelude.prelude.Int
+  
+  type t_T'0
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0)
+    
+   =
+    [%#sfset12] Fset.mem e self
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate contains'1 [#"../../../creusot-contracts/src/logic/seq.rs" 351 4 353 17] (self : Seq.seq t_T'0) (x : t_T'0)
+   =
+    [%#sseq13] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'2 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_T'0) (e : t_T'0)
+    
+   =
+    [%#sfset12] Fset.mem e self
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function insert'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 64 4 64 37] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset19] Fset.add e self
+  
+  function singleton'0 [#"../../../creusot-contracts/src/logic/fset.rs" 201 4 201 34] (x : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset16] insert'0 (Fset.empty  : Fset.fset (Seq.seq t_T'0)) x
+  
+  axiom singleton'0_spec : forall x : Seq.seq t_T'0 . [%#sfset15] forall y : Seq.seq t_T'0 . contains'0 (singleton'0 x) y
+  = (x = y)
+  
+  use seq.Seq
+  
+  function tail'0 [#"../../../creusot-contracts/src/logic/seq.rs" 172 4 172 29] (self : Seq.seq t_T'0) : Seq.seq t_T'0 =
+    [%#sseq20] Seq.([..]) self 1 (Seq.length self)
+  
+  function cons'0 [#"../../../creusot-contracts/src/logic/fset.rs" 248 4 248 61] (s : Fset.fset t_T'0) (ss : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom cons'0_spec : forall s : Fset.fset t_T'0, ss : Fset.fset (Seq.seq t_T'0) . [%#sfset18] forall xs : Seq.seq t_T'0 . contains'0 (cons'0 s ss) xs
+  = (0 < Seq.length xs /\ contains'2 s (Seq.get xs 0) /\ contains'0 ss (tail'0 xs))
+  
+  function replicate'0 [#"../../../creusot-contracts/src/logic/fset.rs" 267 4 267 50] (self : Fset.fset t_T'0) (n : int) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom replicate'0_def : forall self : Fset.fset t_T'0, n : int . ([%#sfset3] n >= 0)
+   -> replicate'0 self n
+  = ([%#sfset10] if n = 0 then
+    let _ = let _ = () in () in singleton'0 (Seq.empty  : Seq.seq t_T'0)
+  else
+    let _ = let _ = () in () in cons'0 self (replicate'0 self (n - 1))
+  )
+  
+  axiom replicate'0_spec : forall self : Fset.fset t_T'0, n : int . ([%#sfset3] n >= 0)
+   -> ([%#sfset4] forall xs : Seq.seq t_T'0 . contains'0 (replicate'0 self n) xs
+  = (Seq.length xs = n /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x)))
+  
+  use seq.Seq
+  
+  function concat'0 [#"../../../creusot-contracts/src/logic/fset.rs" 257 4 257 67] (s : Fset.fset (Seq.seq t_T'0)) (t : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom concat'0_spec : forall s : Fset.fset (Seq.seq t_T'0), t : Fset.fset (Seq.seq t_T'0) . [%#sfset11] forall xs : Seq.seq t_T'0 . contains'0 (concat'0 s t) xs
+  = (exists ys : Seq.seq t_T'0, zs : Seq.seq t_T'0 . contains'0 s ys /\ contains'0 t zs /\ xs = Seq.(++) ys zs)
+  
+  function concat_empty'0 [#"../../../creusot-contracts/src/logic/fset.rs" 518 0 518 39] (s : Fset.fset (Seq.seq t_T'0)) : ()
+    
+   =
+    [%#sfset14] let _ = let _ = () in () in let _ = let _ = () in () in ()
+  
+  axiom concat_empty'0_spec : forall s : Fset.fset (Seq.seq t_T'0) . ([%#sfset6] concat'0 (singleton'0 (Seq.empty  : Seq.seq t_T'0)) s
+  = s)
+  && ([%#sfset7] concat'0 s (singleton'0 (Seq.empty  : Seq.seq t_T'0)) = s)
+  
+  function cons_concat'0 [#"../../../creusot-contracts/src/logic/fset.rs" 490 0 490 23] (_1 : ()) : () =
+    [%#sfset17] let _ = let _ = () in () in let _ = let _ = () in () in let _ = let _ = () in () in ()
+  
+  axiom cons_concat'0_spec : forall _1 : () . [%#sfset8] forall s : Fset.fset t_T'0, t : Fset.fset (Seq.seq t_T'0), u : Fset.fset (Seq.seq t_T'0) . concat'0 (cons'0 s t) u
+  = cons'0 s (concat'0 t u)
+  
+  constant n  : int
+  
+  constant m  : int
+  
+  constant s  : Fset.fset t_T'0
+  
+  function concat_replicate'0 [#"../../../creusot-contracts/src/logic/fset.rs" 502 0 502 54] (n : int) (m : int) (s : Fset.fset t_T'0) : ()
+    
+  
+  goal vc_concat_replicate'0 : ([%#sfset0] 0 <= n /\ 0 <= m)
+   -> (if n = 0 then
+    ([@expl:replicate requires] [%#sfset3] m >= 0)
+    /\ (([%#sfset4] forall xs : Seq.seq t_T'0 . contains'0 (replicate'0 s m) xs
+    = (Seq.length xs = m /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 s x)))
+     -> ([%#sfset6] concat'0 (singleton'0 (Seq.empty  : Seq.seq t_T'0)) (replicate'0 s m) = replicate'0 s m)
+    && ([%#sfset7] concat'0 (replicate'0 s m) (singleton'0 (Seq.empty  : Seq.seq t_T'0)) = replicate'0 s m)
+     -> (let _ = concat_empty'0 (replicate'0 s m) in [%#sfset1] replicate'0 s (n + m)
+    = concat'0 (replicate'0 s n) (replicate'0 s m)))
+  else
+    ([%#sfset8] forall s : Fset.fset t_T'0, t : Fset.fset (Seq.seq t_T'0), u : Fset.fset (Seq.seq t_T'0) . concat'0 (cons'0 s t) u
+    = cons'0 s (concat'0 t u))
+     -> (let _ = cons_concat'0 () in (([@expl:concat_replicate requires] [%#sfset0] 0 <= n - 1 /\ 0 <= m)
+    /\ 0 <= ([%#sfset2] n) /\ ([%#sfset2] n - 1) < ([%#sfset2] n))
+    /\ (([%#sfset1] replicate'0 s (n - 1 + m) = concat'0 (replicate'0 s (n - 1)) (replicate'0 s m))
+     -> (let _ = concat_replicate'0 (n - 1) m s in [%#sfset1] replicate'0 s (n + m)
+    = concat'0 (replicate'0 s n) (replicate'0 s m))))
+  )
+end
+module M_creusot_contracts__logic__fset__concat_empty [#"../../../creusot-contracts/src/logic/fset.rs" 518 0 518 39]
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 516 10 516 59
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 517 10 517 59
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 519 20 519 66
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 520 20 520 66
+  let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 519 4 519 68
+  let%span sfset5 = "../../../creusot-contracts/src/logic/fset.rs" 200 14 200 57
+  let%span sfset6 = "../../../creusot-contracts/src/logic/fset.rs" 202 8 202 29
+  let%span sfset7 = "../../../creusot-contracts/src/logic/fset.rs" 256 14 256 144
+  let%span sfset8 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  let%span sfset9 = "../../../creusot-contracts/src/logic/fset.rs" 65 8 65 26
+  
+  use seq.Seq
+  
+  type t_T'0
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0)
+    
+   =
+    [%#sfset8] Fset.mem e self
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function insert'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 64 4 64 37] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset9] Fset.add e self
+  
+  function singleton'0 [#"../../../creusot-contracts/src/logic/fset.rs" 201 4 201 34] (x : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset6] insert'0 (Fset.empty  : Fset.fset (Seq.seq t_T'0)) x
+  
+  axiom singleton'0_spec : forall x : Seq.seq t_T'0 . [%#sfset5] forall y : Seq.seq t_T'0 . contains'0 (singleton'0 x) y
+  = (x = y)
+  
+  use seq.Seq
+  
+  function concat'0 [#"../../../creusot-contracts/src/logic/fset.rs" 257 4 257 67] (s : Fset.fset (Seq.seq t_T'0)) (t : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom concat'0_spec : forall s : Fset.fset (Seq.seq t_T'0), t : Fset.fset (Seq.seq t_T'0) . [%#sfset7] forall xs : Seq.seq t_T'0 . contains'0 (concat'0 s t) xs
+  = (exists ys : Seq.seq t_T'0, zs : Seq.seq t_T'0 . contains'0 s ys /\ contains'0 t zs /\ xs = Seq.(++) ys zs)
+  
+  constant s  : Fset.fset (Seq.seq t_T'0)
+  
+  function concat_empty'0 [#"../../../creusot-contracts/src/logic/fset.rs" 518 0 518 39] (s : Fset.fset (Seq.seq t_T'0)) : ()
+    
+  
+  goal vc_concat_empty'0 : ([%#sfset2] forall xs : Seq.seq t_T'0 . Seq.(++) xs (Seq.empty  : Seq.seq t_T'0) = xs)
+  && (let _ = () in let _ = () in ([%#sfset3] forall xs : Seq.seq t_T'0 . Seq.(++) (Seq.empty  : Seq.seq t_T'0) xs = xs)
+  && (let _ = () in let _ = () in ([%#sfset0] concat'0 (singleton'0 (Seq.empty  : Seq.seq t_T'0)) s = s)
+  && ([%#sfset1] concat'0 s (singleton'0 (Seq.empty  : Seq.seq t_T'0)) = s)))
+end
+module M_creusot_contracts__logic__fset__concat_replicate_up_to [#"../../../creusot-contracts/src/logic/fset.rs" 530 0 530 60]
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 526 11 526 26
+  let%span sfset1 = "../../../creusot-contracts/src/logic/fset.rs" 527 10 528 67
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 529 10 529 11
+  let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 264 15 264 21
+  let%span sfset4 = "../../../creusot-contracts/src/logic/fset.rs" 265 14 265 123
+  let%span sfset5 = "../../../creusot-contracts/src/logic/fset.rs" 266 14 266 15
+  let%span sfset6 = "../../../creusot-contracts/src/logic/fset.rs" 516 10 516 59
+  let%span sfset7 = "../../../creusot-contracts/src/logic/fset.rs" 517 10 517 59
+  let%span sfset8 = "../../../creusot-contracts/src/logic/fset.rs" 480 10 481 83
+  let%span sfset9 = "../../../creusot-contracts/src/logic/fset.rs" 482 10 483 83
+  let%span sfset10 = "../../../creusot-contracts/src/logic/fset.rs" 499 11 499 27
+  let%span sfset11 = "../../../creusot-contracts/src/logic/fset.rs" 500 10 500 76
+  let%span sfset12 = "../../../creusot-contracts/src/logic/fset.rs" 501 10 501 11
+  let%span sfset13 = "../../../creusot-contracts/src/logic/fset.rs" 531 4 539 5
+  let%span sfset14 = "../../../creusot-contracts/src/logic/fset.rs" 282 15 282 21
+  let%span sfset15 = "../../../creusot-contracts/src/logic/fset.rs" 283 14 283 123
+  let%span sfset16 = "../../../creusot-contracts/src/logic/fset.rs" 284 14 284 15
+  let%span sfset17 = "../../../creusot-contracts/src/logic/fset.rs" 286 8 293 9
+  let%span sfset18 = "../../../creusot-contracts/src/logic/fset.rs" 268 8 276 9
+  let%span sfset19 = "../../../creusot-contracts/src/logic/fset.rs" 256 14 256 144
+  let%span sfset20 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  let%span sseq21 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
+  let%span sfset22 = "../../../creusot-contracts/src/logic/fset.rs" 519 4 519 68
+  let%span sfset23 = "../../../creusot-contracts/src/logic/fset.rs" 200 14 200 57
+  let%span sfset24 = "../../../creusot-contracts/src/logic/fset.rs" 202 8 202 29
+  let%span sfset25 = "../../../creusot-contracts/src/logic/fset.rs" 478 0 478 8
+  let%span sfset26 = "../../../creusot-contracts/src/logic/fset.rs" 503 4 510 5
+  let%span sfset27 = "../../../creusot-contracts/src/logic/fset.rs" 247 14 247 117
+  let%span sfset28 = "../../../creusot-contracts/src/logic/fset.rs" 65 8 65 26
+  let%span sfset29 = "../../../creusot-contracts/src/logic/fset.rs" 489 10 489 133
+  let%span sfset30 = "../../../creusot-contracts/src/logic/fset.rs" 491 4 491 117
+  let%span sseq31 = "../../../creusot-contracts/src/logic/seq.rs" 173 8 173 39
+  
+  use prelude.prelude.Int
+  
+  type t_T'0
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0)
+    
+   =
+    [%#sfset20] Fset.mem e self
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate contains'1 [#"../../../creusot-contracts/src/logic/seq.rs" 351 4 353 17] (self : Seq.seq t_T'0) (x : t_T'0)
+   =
+    [%#sseq21] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'2 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 45 4 45 39] (self : Fset.fset t_T'0) (e : t_T'0)
+    
+   =
+    [%#sfset20] Fset.mem e self
+  
+  use seq.Seq
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function insert'0 [@inline:trivial] [#"../../../creusot-contracts/src/logic/fset.rs" 64 4 64 37] (self : Fset.fset (Seq.seq t_T'0)) (e : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset28] Fset.add e self
+  
+  function singleton'0 [#"../../../creusot-contracts/src/logic/fset.rs" 201 4 201 34] (x : Seq.seq t_T'0) : Fset.fset (Seq.seq t_T'0)
+    
+   =
+    [%#sfset24] insert'0 (Fset.empty  : Fset.fset (Seq.seq t_T'0)) x
+  
+  axiom singleton'0_spec : forall x : Seq.seq t_T'0 . [%#sfset23] forall y : Seq.seq t_T'0 . contains'0 (singleton'0 x) y
+  = (x = y)
+  
+  use seq.Seq
+  
+  function tail'0 [#"../../../creusot-contracts/src/logic/seq.rs" 172 4 172 29] (self : Seq.seq t_T'0) : Seq.seq t_T'0 =
+    [%#sseq31] Seq.([..]) self 1 (Seq.length self)
+  
+  function cons'0 [#"../../../creusot-contracts/src/logic/fset.rs" 248 4 248 61] (s : Fset.fset t_T'0) (ss : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom cons'0_spec : forall s : Fset.fset t_T'0, ss : Fset.fset (Seq.seq t_T'0) . [%#sfset27] forall xs : Seq.seq t_T'0 . contains'0 (cons'0 s ss) xs
+  = (0 < Seq.length xs /\ contains'2 s (Seq.get xs 0) /\ contains'0 ss (tail'0 xs))
+  
+  function replicate'0 [#"../../../creusot-contracts/src/logic/fset.rs" 267 4 267 50] (self : Fset.fset t_T'0) (n : int) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom replicate'0_def : forall self : Fset.fset t_T'0, n : int . ([%#sfset3] n >= 0)
+   -> replicate'0 self n
+  = ([%#sfset18] if n = 0 then
+    let _ = let _ = () in () in singleton'0 (Seq.empty  : Seq.seq t_T'0)
+  else
+    let _ = let _ = () in () in cons'0 self (replicate'0 self (n - 1))
+  )
+  
+  axiom replicate'0_spec : forall self : Fset.fset t_T'0, n : int . ([%#sfset3] n >= 0)
+   -> ([%#sfset4] forall xs : Seq.seq t_T'0 . contains'0 (replicate'0 self n) xs
+  = (Seq.length xs = n /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x)))
+  
+  use set.Fset
+  
+  function replicate_up_to'0 [#"../../../creusot-contracts/src/logic/fset.rs" 285 4 285 56] (self : Fset.fset t_T'0) (n : int) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom replicate_up_to'0_def : forall self : Fset.fset t_T'0, n : int . ([%#sfset14] n >= 0)
+   -> replicate_up_to'0 self n
+  = ([%#sfset17] if n = 0 then
+    let _ = let _ = () in () in singleton'0 (Seq.empty  : Seq.seq t_T'0)
+  else
+    Fset.union (replicate_up_to'0 self (n - 1)) (replicate'0 self n)
+  )
+  
+  axiom replicate_up_to'0_spec : forall self : Fset.fset t_T'0, n : int . ([%#sfset14] n >= 0)
+   -> ([%#sfset15] forall xs : Seq.seq t_T'0 . contains'0 (replicate_up_to'0 self n) xs
+  = (Seq.length xs <= n /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 self x)))
+  
+  use seq.Seq
+  
+  function concat'0 [#"../../../creusot-contracts/src/logic/fset.rs" 257 4 257 67] (s : Fset.fset (Seq.seq t_T'0)) (t : Fset.fset (Seq.seq t_T'0)) : Fset.fset (Seq.seq t_T'0)
+    
+  
+  axiom concat'0_spec : forall s : Fset.fset (Seq.seq t_T'0), t : Fset.fset (Seq.seq t_T'0) . [%#sfset19] forall xs : Seq.seq t_T'0 . contains'0 (concat'0 s t) xs
+  = (exists ys : Seq.seq t_T'0, zs : Seq.seq t_T'0 . contains'0 s ys /\ contains'0 t zs /\ xs = Seq.(++) ys zs)
+  
+  function concat_empty'0 [#"../../../creusot-contracts/src/logic/fset.rs" 518 0 518 39] (s : Fset.fset (Seq.seq t_T'0)) : ()
+    
+   =
+    [%#sfset22] let _ = let _ = () in () in let _ = let _ = () in () in ()
+  
+  axiom concat_empty'0_spec : forall s : Fset.fset (Seq.seq t_T'0) . ([%#sfset6] concat'0 (singleton'0 (Seq.empty  : Seq.seq t_T'0)) s
+  = s)
+  && ([%#sfset7] concat'0 s (singleton'0 (Seq.empty  : Seq.seq t_T'0)) = s)
+  
+  function concat_union'0 [#"../../../creusot-contracts/src/logic/fset.rs" 484 0 484 24] (_1 : ()) : () =
+    [%#sfset25] ()
+  
+  axiom concat_union'0_spec : forall _1 : () . ([%#sfset8] forall s1 : Fset.fset (Seq.seq t_T'0), s2 : Fset.fset (Seq.seq t_T'0), t : Fset.fset (Seq.seq t_T'0) . concat'0 (Fset.union s1 s2) t
+  = Fset.union (concat'0 s1 t) (concat'0 s2 t))
+  && ([%#sfset9] forall s : Fset.fset (Seq.seq t_T'0), t1 : Fset.fset (Seq.seq t_T'0), t2 : Fset.fset (Seq.seq t_T'0) . concat'0 s (Fset.union t1 t2)
+  = Fset.union (concat'0 s t1) (concat'0 s t2))
+  
+  function cons_concat'0 [#"../../../creusot-contracts/src/logic/fset.rs" 490 0 490 23] (_1 : ()) : () =
+    [%#sfset30] let _ = let _ = () in () in let _ = let _ = () in () in let _ = let _ = () in () in ()
   
-  predicate inv'3 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Option'0)
+  axiom cons_concat'0_spec : forall _1 : () . [%#sfset29] forall s : Fset.fset t_T'0, t : Fset.fset (Seq.seq t_T'0), u : Fset.fset (Seq.seq t_T'0) . concat'0 (cons'0 s t) u
+  = cons'0 s (concat'0 t u)
   
-  axiom inv_axiom'3 [@rewrite] : forall x : t_Option'0 [inv'3 x] . inv'3 x = invariant'2 x
+  function concat_replicate'0 [#"../../../creusot-contracts/src/logic/fset.rs" 502 0 502 54] (n : int) (m : int) (s : Fset.fset t_T'0) : ()
+    
   
-  let rec is_some'0 (self:t_Option'0) (return'  (ret:bool))= {[@expl:is_some 'self' type invariant] inv'3 self}
-    any [ return' (result:bool)-> {[%#soption7] result = (self <> C_None'0)} (! return' {result}) ] 
+  axiom concat_replicate'0_def : forall n : int, m : int, s : Fset.fset t_T'0 . ([%#sfset10] 0 <= n /\ 0 <= m)
+   -> concat_replicate'0 n m s
+  = ([%#sfset26] if n = 0 then
+    let _ = concat_empty'0 (replicate'0 s m) in ()
+  else
+    let _ = cons_concat'0 () in let _ = concat_replicate'0 (n - 1) m s in ()
+  )
   
-  use prelude.prelude.Intrinsic
+  axiom concat_replicate'0_spec : forall n : int, m : int, s : Fset.fset t_T'0 . ([%#sfset10] 0 <= n /\ 0 <= m)
+   -> ([%#sfset11] replicate'0 s (n + m) = concat'0 (replicate'0 s n) (replicate'0 s m))
   
-  meta "compute_max_steps" 1000000
+  constant n  : int
   
-  let rec contains_ghost'0 (self:t_FMap'0) (key:t_K'0) (return'  (ret:bool))= {[@expl:contains_ghost 'self' type invariant] [%#sfmap0] inv'0 self}
-    {[@expl:contains_ghost 'key' type invariant] [%#sfmap1] inv'1 key}
-    (! bb0
-    [ bb0 = s0 [ s0 = get_ghost'0 {self} {key} (fun (_ret':t_Option'0) ->  [ &_5 <- _ret' ] s1) | s1 = bb1 ] 
-    | bb1 = s0 [ s0 = is_some'0 {_5} (fun (_ret':bool) ->  [ &_0 <- _ret' ] s1) | s1 = bb2 ] 
-    | bb2 = return' {_0} ]
-    ) [ & _0 : bool = any_l () | & self : t_FMap'0 = self | & key : t_K'0 = key | & _5 : t_Option'0 = any_l () ] 
-    [ return' (result:bool)-> {[@expl:contains_ghost ensures] [%#sfmap2] result = contains'0 self key}
-      (! return' {result}) ]
+  constant m  : int
+  
+  constant s  : Fset.fset t_T'0
+  
+  function concat_replicate_up_to'0 [#"../../../creusot-contracts/src/logic/fset.rs" 530 0 530 60] (n : int) (m : int) (s : Fset.fset t_T'0) : ()
     
+  
+  goal vc_concat_replicate_up_to'0 : ([%#sfset0] 0 <= n /\ n < m)
+   -> (if n + 1 = m then
+    ([@expl:replicate requires] [%#sfset3] n + 1 >= 0)
+    /\ (([%#sfset4] forall xs : Seq.seq t_T'0 . contains'0 (replicate'0 s (n + 1)) xs
+    = (Seq.length xs = n + 1 /\ (forall x : t_T'0 . contains'1 xs x  -> contains'2 s x)))
+     -> ([%#sfset6] concat'0 (singleton'0 (Seq.empty  : Seq.seq t_T'0)) (replicate'0 s (n + 1)) = replicate'0 s (n + 1))
+    && ([%#sfset7] concat'0 (replicate'0 s (n + 1)) (singleton'0 (Seq.empty  : Seq.seq t_T'0)) = replicate'0 s (n + 1))
+     -> (let _ = concat_empty'0 (replicate'0 s (n + 1)) in [%#sfset1] replicate_up_to'0 s m
+    = Fset.union (replicate_up_to'0 s n) (concat'0 (replicate'0 s (n + 1)) (replicate_up_to'0 s (m - n - 1)))))
+  else
+    ([%#sfset8] forall s1 : Fset.fset (Seq.seq t_T'0), s2 : Fset.fset (Seq.seq t_T'0), t : Fset.fset (Seq.seq t_T'0) . concat'0 (Fset.union s1 s2) t
+    = Fset.union (concat'0 s1 t) (concat'0 s2 t))
+    && ([%#sfset9] forall s : Fset.fset (Seq.seq t_T'0), t1 : Fset.fset (Seq.seq t_T'0), t2 : Fset.fset (Seq.seq t_T'0) . concat'0 s (Fset.union t1 t2)
+    = Fset.union (concat'0 s t1) (concat'0 s t2))
+     -> (let _ = concat_union'0 () in ([@expl:concat_replicate requires] [%#sfset10] 0 <= n /\ 0 <= m - n - 1)
+    /\ (([%#sfset11] replicate'0 s (n + (m - n - 1)) = concat'0 (replicate'0 s n) (replicate'0 s (m - n - 1)))
+     -> (let _ = concat_replicate'0 n (m - n - 1) s in (([@expl:concat_replicate_up_to requires] [%#sfset0] 0 <= n
+    /\ n < m - 1)
+    /\ 0 <= ([%#sfset2] m) /\ ([%#sfset2] m - 1) < ([%#sfset2] m))
+    /\ (([%#sfset1] replicate_up_to'0 s (m - 1)
+    = Fset.union (replicate_up_to'0 s n) (concat'0 (replicate'0 s (n + 1)) (replicate_up_to'0 s (m - 1 - n - 1))))
+     -> (let _ = concat_replicate_up_to'0 n (m - 1) s in [%#sfset1] replicate_up_to'0 s m
+    = Fset.union (replicate_up_to'0 s n) (concat'0 (replicate'0 s (n + 1)) (replicate_up_to'0 s (m - n - 1))))))))
+  )
 end
 module M_creusot_contracts__logic__ord__qyi8355372356285216375__cmp_le_log [#"../../../creusot-contracts/src/logic/ord.rs" 130 8 130 39] (* <logic::int::Int as logic::ord::OrdLogic> *)
   let%span sord0 = "../../../creusot-contracts/src/logic/ord.rs" 129 39 129 89
@@ -19128,10 +20815,10 @@ module M_creusot_contracts__stdqy35z1__collections__hash_map__qyi160525698381677
   goal refines : [%#shash_map0] forall self : t_IterMut'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq (t_K'0, borrowed t_V'0)) self
    -> produces'0 self (Seq.empty  : Seq.seq (t_K'0, borrowed t_V'0)) self
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi2602027177218488890__produces_refl__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 102 4 102 26] (* <std::collections::hash_set::IntoIter<T> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 102 4 102 26
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 90 8 90 38
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi2602027177218488890__produces_refl__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 108 4 108 26] (* <std::collections::hash_set::IntoIter<T> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 108 4 108 26
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 96 8 96 38
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span sseq4 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
   
@@ -19263,7 +20950,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 46 4 46 33] (self : t_IntoIter'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 52 4 52 33] (self : t_IntoIter'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -19287,7 +20974,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
    =
     [%#sseq4] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_IntoIter'0) (visited : Seq.seq t_T'0) (end' : t_IntoIter'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_IntoIter'0) (visited : Seq.seq t_T'0) (end' : t_IntoIter'0)
     
    =
     [%#shash_set2] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -19302,7 +20989,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 89 4 89 64] (self : t_IntoIter'0) (visited : Seq.seq t_T'0) (o : t_IntoIter'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 95 4 95 64] (self : t_IntoIter'0) (visited : Seq.seq t_T'0) (o : t_IntoIter'0)
     
    =
     [%#shash_set1] set_produces'0 self visited o
@@ -19310,10 +20997,10 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
   goal refines : [%#shash_set0] forall self : t_IntoIter'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq t_T'0) self
    -> produces'0 self (Seq.empty  : Seq.seq t_T'0) self
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi2602027177218488890__produces_trans__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 109 4 109 90] (* <std::collections::hash_set::IntoIter<T> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 109 4 109 90
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 90 8 90 38
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi2602027177218488890__produces_trans__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 115 4 115 90] (* <std::collections::hash_set::IntoIter<T> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 115 4 115 90
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 96 8 96 38
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span sseq4 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
   
@@ -19443,7 +21130,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 46 4 46 33] (self : t_IntoIter'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 52 4 52 33] (self : t_IntoIter'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -19467,7 +21154,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
    =
     [%#sseq4] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_IntoIter'0) (visited : Seq.seq t_T'0) (end' : t_IntoIter'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_IntoIter'0) (visited : Seq.seq t_T'0) (end' : t_IntoIter'0)
     
    =
     [%#shash_set2] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -19482,7 +21169,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 89 4 89 64] (self : t_IntoIter'0) (visited : Seq.seq t_T'0) (o : t_IntoIter'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 95 4 95 64] (self : t_IntoIter'0) (visited : Seq.seq t_T'0) (o : t_IntoIter'0)
     
    =
     [%#shash_set1] set_produces'0 self visited o
@@ -19494,10 +21181,10 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi260202717721848
    -> produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (Seq.(++) ab bc) c  -> produces'0 a (Seq.(++) ab bc) c)
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi7331660899108484271__produces_trans__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 148 4 148 90] (* <std::collections::hash_set::Iter<'a, T> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 148 4 148 90
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 129 8 129 38
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi7331660899108484271__produces_trans__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 154 4 154 90] (* <std::collections::hash_set::Iter<'a, T> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 154 4 154 90
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 135 8 135 38
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span smodel4 = "../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span sseq5 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
@@ -19551,7 +21238,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 120 4 120 33] (self : t_Iter'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 126 4 126 33] (self : t_Iter'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -19578,7 +21265,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
    =
     [%#sseq5] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_Iter'0) (visited : Seq.seq t_T'0) (end' : t_Iter'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_Iter'0) (visited : Seq.seq t_T'0) (end' : t_Iter'0)
     
    =
     [%#shash_set2] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -19593,7 +21280,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 128 4 128 64] (self : t_Iter'0) (visited : Seq.seq t_T'0) (o : t_Iter'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 134 4 134 64] (self : t_Iter'0) (visited : Seq.seq t_T'0) (o : t_Iter'0)
     
    =
     [%#shash_set1] set_produces'0 self visited o
@@ -19605,10 +21292,10 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
    -> produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (Seq.(++) ab bc) c  -> produces'0 a (Seq.(++) ab bc) c)
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi7331660899108484271__produces_refl__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 141 4 141 26] (* <std::collections::hash_set::Iter<'a, T> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 141 4 141 26
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 129 8 129 38
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi7331660899108484271__produces_refl__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 147 4 147 26] (* <std::collections::hash_set::Iter<'a, T> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 147 4 147 26
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 135 8 135 38
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span smodel4 = "../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span sseq5 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
@@ -19664,7 +21351,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 120 4 120 33] (self : t_Iter'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 126 4 126 33] (self : t_Iter'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -19691,7 +21378,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
    =
     [%#sseq5] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_Iter'0) (visited : Seq.seq t_T'0) (end' : t_Iter'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_Iter'0) (visited : Seq.seq t_T'0) (end' : t_Iter'0)
     
    =
     [%#shash_set2] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -19706,7 +21393,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 128 4 128 64] (self : t_Iter'0) (visited : Seq.seq t_T'0) (o : t_Iter'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 134 4 134 64] (self : t_Iter'0) (visited : Seq.seq t_T'0) (o : t_Iter'0)
     
    =
     [%#shash_set1] set_produces'0 self visited o
@@ -19714,10 +21401,10 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi733166089910848
   goal refines : [%#shash_set0] forall self : t_Iter'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq t_T'0) self
    -> produces'0 self (Seq.empty  : Seq.seq t_T'0) self
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi3673804955138978513__produces_refl__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 216 4 216 26] (* <std::collections::hash_set::Intersection<'a, T, S> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 216 4 216 26
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 204 8 204 38
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi3673804955138978513__produces_refl__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 222 4 222 26] (* <std::collections::hash_set::Intersection<'a, T, S> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 222 4 222 26
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 210 8 210 38
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span smodel4 = "../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span sseq5 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
@@ -19799,7 +21486,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 195 4 195 33] (self : t_Intersection'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 201 4 201 33] (self : t_Intersection'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -19826,7 +21513,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
    =
     [%#sseq5] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_Intersection'0) (visited : Seq.seq t_T'0) (end' : t_Intersection'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_Intersection'0) (visited : Seq.seq t_T'0) (end' : t_Intersection'0)
     
    =
     [%#shash_set2] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -19841,7 +21528,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 203 4 203 64] (self : t_Intersection'0) (visited : Seq.seq t_T'0) (o : t_Intersection'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 209 4 209 64] (self : t_Intersection'0) (visited : Seq.seq t_T'0) (o : t_Intersection'0)
     
    =
     [%#shash_set1] set_produces'0 self visited o
@@ -19849,10 +21536,10 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
   goal refines : [%#shash_set0] forall self : t_Intersection'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq t_T'0) self
    -> produces'0 self (Seq.empty  : Seq.seq t_T'0) self
 end
-module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi3673804955138978513__produces_trans__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 223 4 223 90] (* <std::collections::hash_set::Intersection<'a, T, S> as std::iter::Iterator> *)
-  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 223 4 223 90
-  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 204 8 204 38
-  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi3673804955138978513__produces_trans__refines [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 229 4 229 90] (* <std::collections::hash_set::Intersection<'a, T, S> as std::iter::Iterator> *)
+  let%span shash_set0 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 229 4 229 90
+  let%span shash_set1 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 210 8 210 38
+  let%span shash_set2 = "../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span smodel4 = "../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span sseq5 = "../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
@@ -19932,7 +21619,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
   
   use set.Fset
   
-  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 195 4 195 33] (self : t_Intersection'0) : Fset.fset t_DeepModelTy'0
+  function view'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 201 4 201 33] (self : t_Intersection'0) : Fset.fset t_DeepModelTy'0
     
   
   use set.Fset
@@ -19959,7 +21646,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
    =
     [%#sseq5] exists i : int . 0 <= i /\ i < Seq.length self /\ Seq.get self i = x
   
-  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 53 0 57 9] (start : t_Intersection'0) (visited : Seq.seq t_T'0) (end' : t_Intersection'0)
+  predicate set_produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 59 0 63 9] (start : t_Intersection'0) (visited : Seq.seq t_T'0) (end' : t_Intersection'0)
     
    =
     [%#shash_set2] Fset.cardinal (view'0 start) = Seq.length visited + Fset.cardinal (view'0 end')
@@ -19974,7 +21661,7 @@ module M_creusot_contracts__stdqy35z1__collections__hash_set__qyi367380495513897
     /\ 0 <= j /\ j < Seq.length visited /\ deep_model'0 (Seq.get visited i) = deep_model'0 (Seq.get visited j)
      -> i = j)
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 203 4 203 64] (self : t_Intersection'0) (visited : Seq.seq t_T'0) (o : t_Intersection'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/collections/hash_set.rs" 209 4 209 64] (self : t_Intersection'0) (visited : Seq.seq t_T'0) (o : t_Intersection'0)
     
    =
     [%#shash_set1] set_produces'0 self visited o
@@ -20158,10 +21845,10 @@ module M_creusot_contracts__stdqy35z1__iter__cloned__qyi10472681371035856984__pr
   let%span scloned0 = "../../../creusot-contracts/src/std/iter/cloned.rs" 65 4 65 90
   let%span scloned1 = "../../../creusot-contracts/src/std/iter/cloned.rs" 48 12 51 79
   let%span scloned2 = "../../../creusot-contracts/src/std/iter/cloned.rs" 11 14 11 39
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -20193,16 +21880,16 @@ module M_creusot_contracts__stdqy35z1__iter__cloned__qyi10472681371035856984__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_T'0, b : t_I'0, bc : Seq.seq t_T'0, c : t_I'0 . ([%#siter4] produces'1 a ab b)
    -> ([%#siter5] produces'1 b bc c)  -> ([%#siter6] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter3] produces'1 self (Seq.empty  : Seq.seq t_T'0) self
   
@@ -20234,10 +21921,10 @@ module M_creusot_contracts__stdqy35z1__iter__cloned__qyi10472681371035856984__pr
   let%span scloned0 = "../../../creusot-contracts/src/std/iter/cloned.rs" 58 4 58 26
   let%span scloned1 = "../../../creusot-contracts/src/std/iter/cloned.rs" 48 12 51 79
   let%span scloned2 = "../../../creusot-contracts/src/std/iter/cloned.rs" 11 14 11 39
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -20271,16 +21958,16 @@ module M_creusot_contracts__stdqy35z1__iter__cloned__qyi10472681371035856984__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_T'0, b : t_I'0, bc : Seq.seq t_T'0, c : t_I'0 . ([%#siter4] produces'1 a ab b)
    -> ([%#siter5] produces'1 b bc c)  -> ([%#siter6] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter3] produces'1 self (Seq.empty  : Seq.seq t_T'0) self
   
@@ -20308,10 +21995,10 @@ module M_creusot_contracts__stdqy35z1__iter__copied__qyi18224474876607687026__pr
   let%span scopied0 = "../../../creusot-contracts/src/std/iter/copied.rs" 58 4 58 26
   let%span scopied1 = "../../../creusot-contracts/src/std/iter/copied.rs" 48 12 51 79
   let%span scopied2 = "../../../creusot-contracts/src/std/iter/copied.rs" 11 14 11 39
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -20345,16 +22032,16 @@ module M_creusot_contracts__stdqy35z1__iter__copied__qyi18224474876607687026__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_T'0, b : t_I'0, bc : Seq.seq t_T'0, c : t_I'0 . ([%#siter4] produces'1 a ab b)
    -> ([%#siter5] produces'1 b bc c)  -> ([%#siter6] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter3] produces'1 self (Seq.empty  : Seq.seq t_T'0) self
   
@@ -20382,10 +22069,10 @@ module M_creusot_contracts__stdqy35z1__iter__copied__qyi18224474876607687026__pr
   let%span scopied0 = "../../../creusot-contracts/src/std/iter/copied.rs" 65 4 65 90
   let%span scopied1 = "../../../creusot-contracts/src/std/iter/copied.rs" 48 12 51 79
   let%span scopied2 = "../../../creusot-contracts/src/std/iter/copied.rs" 11 14 11 39
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -20417,16 +22104,16 @@ module M_creusot_contracts__stdqy35z1__iter__copied__qyi18224474876607687026__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_T'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_T'0) (b : t_I'0) (bc : Seq.seq t_T'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_T'0, b : t_I'0, bc : Seq.seq t_T'0, c : t_I'0 . ([%#siter4] produces'1 a ab b)
    -> ([%#siter5] produces'1 b bc c)  -> ([%#siter6] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter3] produces'1 self (Seq.empty  : Seq.seq t_T'0) self
   
@@ -20504,10 +22191,10 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   let%span senumerate0 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 90 4 90 90
   let%span senumerate1 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 72 12 76 113
   let%span senumerate2 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 14 14 14 39
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span senumerate7 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 45 12 49 85
   
   type t_I'0
@@ -20533,16 +22220,16 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter4] produces'1 a ab b)
    -> ([%#siter5] produces'1 b bc c)  -> ([%#siter6] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter3] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -20554,7 +22241,7 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   
   use prelude.prelude.Borrow
   
-  predicate completed'0 [#"../../../creusot-contracts/src/std/iter.rs" 35 4 35 36] (self : borrowed t_I'0)
+  predicate completed'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 36] (self : borrowed t_I'0)
   
   predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
   
@@ -20600,10 +22287,10 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   let%span senumerate0 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 83 4 83 26
   let%span senumerate1 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 72 12 76 113
   let%span senumerate2 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 14 14 14 39
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span senumerate7 = "../../../creusot-contracts/src/std/iter/enumerate.rs" 45 12 49 85
   
   type t_I'0
@@ -20631,16 +22318,16 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter4] produces'1 a ab b)
    -> ([%#siter5] produces'1 b bc c)  -> ([%#siter6] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter3] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -20652,7 +22339,7 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   
   use prelude.prelude.Borrow
   
-  predicate completed'0 [#"../../../creusot-contracts/src/std/iter.rs" 35 4 35 36] (self : borrowed t_I'0)
+  predicate completed'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 36] (self : borrowed t_I'0)
   
   predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
   
@@ -20690,9 +22377,9 @@ module M_creusot_contracts__stdqy35z1__iter__enumerate__qyi2718914205750388896__
   goal refines : [%#senumerate0] forall self : t_Enumerate'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq (usize, t_Item'0)) self
    -> produces'0 self (Seq.empty  : Seq.seq (usize, t_Item'0)) self
 end
-module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__produces_refl__refines [#"../../../creusot-contracts/src/std/iter/filter.rs" 106 4 106 26] (* <std::iter::Filter<I, F> as std::iter::Iterator> *)
-  let%span sfilter0 = "../../../creusot-contracts/src/std/iter/filter.rs" 106 4 106 26
-  let%span sfilter1 = "../../../creusot-contracts/src/std/iter/filter.rs" 87 12 99 17
+module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__produces_refl__refines [#"../../../creusot-contracts/src/std/iter/filter.rs" 105 4 105 26] (* <std::iter::Filter<I, F> as std::iter::Iterator> *)
+  let%span sfilter0 = "../../../creusot-contracts/src/std/iter/filter.rs" 105 4 105 26
+  let%span sfilter1 = "../../../creusot-contracts/src/std/iter/filter.rs" 87 12 98 143
   let%span sfilter2 = "../../../creusot-contracts/src/std/iter/filter.rs" 34 12 40 124
   let%span sfilter3 = "../../../creusot-contracts/src/std/iter/filter.rs" 22 14 22 39
   let%span sfilter4 = "../../../creusot-contracts/src/std/iter/filter.rs" 15 14 15 39
@@ -20703,10 +22390,10 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -20789,16 +22476,16 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter13] produces'1 a ab b)
    -> ([%#siter14] produces'1 b bc c)  -> ([%#siter15] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter12] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -20814,8 +22501,8 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
     [%#sfilter1] invariant'0 self
      -> unnest'0 (func'0 self) (func'0 succ)
     /\ (exists s : Seq.seq t_Item'0, f : Map.map int int . produces'1 (iter'0 self) s (iter'0 succ)
-    /\ (forall i : int, j : int . 0 <= i /\ i <= j /\ j < Seq.length visited
-     -> 0 <= Map.get f i /\ Map.get f i <= Map.get f j /\ Map.get f j < Seq.length s)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
     /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> Seq.get visited i = Seq.get s (Map.get f i))
     /\ (forall i : int . 0 <= i /\ i < Seq.length s
      -> (exists j : int . 0 <= j /\ j < Seq.length visited /\ Map.get f j = i)
@@ -20824,9 +22511,9 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   goal refines : [%#sfilter0] forall self : t_Filter'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
    -> produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
 end
-module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__produces_trans__refines [#"../../../creusot-contracts/src/std/iter/filter.rs" 113 4 113 90] (* <std::iter::Filter<I, F> as std::iter::Iterator> *)
-  let%span sfilter0 = "../../../creusot-contracts/src/std/iter/filter.rs" 113 4 113 90
-  let%span sfilter1 = "../../../creusot-contracts/src/std/iter/filter.rs" 87 12 99 17
+module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__produces_trans__refines [#"../../../creusot-contracts/src/std/iter/filter.rs" 112 4 112 90] (* <std::iter::Filter<I, F> as std::iter::Iterator> *)
+  let%span sfilter0 = "../../../creusot-contracts/src/std/iter/filter.rs" 112 4 112 90
+  let%span sfilter1 = "../../../creusot-contracts/src/std/iter/filter.rs" 87 12 98 143
   let%span sfilter2 = "../../../creusot-contracts/src/std/iter/filter.rs" 34 12 40 124
   let%span sfilter3 = "../../../creusot-contracts/src/std/iter/filter.rs" 22 14 22 39
   let%span sfilter4 = "../../../creusot-contracts/src/std/iter/filter.rs" 15 14 15 39
@@ -20837,10 +22524,10 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -20857,18 +22544,329 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   
   predicate precondition'0 [#"../../../creusot-contracts/src/std/ops.rs" 77 4 77 45] (self : t_F'0) (args : t_Item'0)
   
-  predicate postcondition_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 85 4 85 73] (self : t_F'0) (args : t_Item'0) (result : bool)
+  predicate postcondition_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 85 4 85 73] (self : t_F'0) (args : t_Item'0) (result : bool)
+    
+  
+  predicate resolve'0 [#"../../../creusot-contracts/src/resolve.rs" 19 0 19 40] (_1 : t_F'0)
+  
+  predicate postcondition_mut'0 [#"../../../creusot-contracts/src/std/ops.rs" 95 4 95 92] (self : t_F'0) (args : t_Item'0) (result_state : t_F'0) (result : bool)
+    
+  
+  function fn_mut_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 129 4 129 55] (self : t_F'0) (args : t_Item'0) (res : bool) : ()
+    
+  
+  axiom fn_mut_once'0_spec : forall self : t_F'0, args : t_Item'0, res : bool . [%#sops11] postcondition_once'0 self args res
+  = (exists res_state : t_F'0 . postcondition_mut'0 self args res_state res /\ resolve'0 res_state)
+  
+  predicate unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 103 4 103 36] (self : t_F'0) (_2 : t_F'0)
+  
+  function unnest_trans'0 [#"../../../creusot-contracts/src/std/ops.rs" 123 4 123 43] (self : t_F'0) (b : t_F'0) (c : t_F'0) : ()
+    
+  
+  axiom unnest_trans'0_spec : forall self : t_F'0, b : t_F'0, c : t_F'0 . ([%#sops8] unnest'0 self b)
+   -> ([%#sops9] unnest'0 b c)  -> ([%#sops10] unnest'0 self c)
+  
+  function unnest_refl'0 [#"../../../creusot-contracts/src/std/ops.rs" 116 4 116 24] (self : t_F'0) : ()
+  
+  axiom unnest_refl'0_spec : forall self : t_F'0 . [%#sops7] unnest'0 self self
+  
+  function postcondition_mut_unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 111 4 111 85] (self : t_F'0) (args : t_Item'0) (res_state : t_F'0) (res : bool) : ()
+    
+  
+  axiom postcondition_mut_unnest'0_spec : forall self : t_F'0, args : t_Item'0, res_state : t_F'0, res : bool . ([%#sops5] postcondition_mut'0 self args res_state res)
+   -> ([%#sops6] unnest'0 self res_state)
+  
+  predicate invariant'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 31 4 31 30] (self : t_Filter'0) =
+    [%#sfilter2] forall f : t_F'0, i : t_Item'0 . precondition'0 f (i)
+    /\ (forall f : t_F'0, g : t_F'0 . unnest'0 f g  -> f = g)
+    /\ (forall f1 : t_F'0, f2 : t_F'0, i : t_Item'0 . not (postcondition_mut'0 f1 (i) f2 true
+    /\ postcondition_mut'0 f1 (i) f2 false))
+  
+  predicate inv'2 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
+  
+  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_F'0)
+  
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Filter'0)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_Filter'0 [inv'0 x] . inv'0 x
+  = (invariant'0 x
+  /\ match x with
+    | {t_Filter__iter'0 = iter ; t_Filter__predicate'0 = predicate'} -> inv'2 iter /\ inv'1 predicate'
+    end)
+  
+  function func'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 23 4 23 22] (self : t_Filter'0) : t_F'0
+  
+  axiom func'0_spec : forall self : t_Filter'0 . [%#sfilter3] inv'0 self  -> inv'1 (func'0 self)
+  
+  use prelude.prelude.Int
+  
+  use map.Map
+  
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 16 4 16 22] (self : t_Filter'0) : t_I'0
+  
+  axiom iter'0_spec : forall self : t_Filter'0 . [%#sfilter4] inv'0 self  -> inv'2 (iter'0 self)
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+    
+  
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+    
+  
+  axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter13] produces'1 a ab b)
+   -> ([%#siter14] produces'1 b bc c)  -> ([%#siter15] produces'1 a (Seq.(++) ab bc) c)
+  
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
+  
+  axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter12] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
+  
+  use seq.Seq
+  
+  use map.Map
+  
+  use seq.Seq
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 85 4 85 67] (self : t_Filter'0) (visited : Seq.seq t_Item'0) (succ : t_Filter'0)
+    
+   =
+    [%#sfilter1] invariant'0 self
+     -> unnest'0 (func'0 self) (func'0 succ)
+    /\ (exists s : Seq.seq t_Item'0, f : Map.map int int . produces'1 (iter'0 self) s (iter'0 succ)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> Seq.get visited i = Seq.get s (Map.get f i))
+    /\ (forall i : int . 0 <= i /\ i < Seq.length s
+     -> (exists j : int . 0 <= j /\ j < Seq.length visited /\ Map.get f j = i)
+    = postcondition_mut'0 (func'0 self) (Seq.get s i) (func'0 self) true))
+  
+  goal refines : [%#sfilter0] forall a : t_Filter'0 . forall ab : Seq.seq t_Item'0 . forall b : t_Filter'0 . forall bc : Seq.seq t_Item'0 . forall c : t_Filter'0 . produces'0 b bc c
+  /\ produces'0 a ab b
+   -> produces'0 b bc c
+  /\ produces'0 a ab b /\ (forall result : () . produces'0 a (Seq.(++) ab bc) c  -> produces'0 a (Seq.(++) ab bc) c)
+end
+module M_creusot_contracts__stdqy35z1__iter__filter_map__qyi13601925333174091585__produces_refl__refines [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 105 4 105 26] (* <std::iter::FilterMap<I, F> as std::iter::Iterator> *)
+  let%span sfilter_map0 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 105 4 105 26
+  let%span sfilter_map1 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 85 12 98 148
+  let%span sfilter_map2 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 34 12 38 32
+  let%span sfilter_map3 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 22 14 22 39
+  let%span sfilter_map4 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 15 14 15 39
+  let%span sfilter_map5 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 48 16 48 50
+  let%span sfilter_map6 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 56 16 56 52
+  let%span sfilter_map7 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 63 16 63 135
+  let%span sops8 = "../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
+  let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 110 14 110 36
+  let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 115 14 115 31
+  let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 120 15 120 29
+  let%span sops12 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
+  let%span sops13 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
+  let%span sops14 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
+  
+  type t_I'0
+  
+  type t_F'0
+  
+  type t_FilterMap'0  =
+    { t_FilterMap__iter'0: t_I'0; t_FilterMap__f'0: t_F'0 }
+  
+  use seq.Seq
+  
+  type t_B'0
+  
+  use seq.Seq
+  
+  predicate inv'2 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
+  
+  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_F'0)
+  
+  type t_Item'0
+  
+  predicate precondition'0 [#"../../../creusot-contracts/src/std/ops.rs" 77 4 77 45] (self : t_F'0) (args : t_Item'0)
+  
+  predicate no_precondition'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 47 0 47 68] (f : t_F'0) =
+    [%#sfilter_map5] forall i : t_Item'0 . precondition'0 f (i)
+  
+  type t_Option'0  =
+    | C_None'0
+    | C_Some'0 t_B'0
+  
+  predicate postcondition_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 85 4 85 73] (self : t_F'0) (args : t_Item'0) (result : t_Option'0)
+    
+  
+  use prelude.prelude.Borrow
+  
+  predicate resolve'0 [#"../../../creusot-contracts/src/resolve.rs" 19 0 19 40] (_1 : t_F'0)
+  
+  predicate postcondition_mut'0 [#"../../../creusot-contracts/src/std/ops.rs" 95 4 95 92] (self : t_F'0) (args : t_Item'0) (result_state : t_F'0) (result : t_Option'0)
+    
+  
+  function fn_mut_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 129 4 129 55] (self : t_F'0) (args : t_Item'0) (res : t_Option'0) : ()
+    
+  
+  axiom fn_mut_once'0_spec : forall self : t_F'0, args : t_Item'0, res : t_Option'0 . [%#sops14] postcondition_once'0 self args res
+  = (exists res_state : t_F'0 . postcondition_mut'0 self args res_state res /\ resolve'0 res_state)
+  
+  predicate unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 103 4 103 36] (self : t_F'0) (_2 : t_F'0)
+  
+  function unnest_trans'0 [#"../../../creusot-contracts/src/std/ops.rs" 123 4 123 43] (self : t_F'0) (b : t_F'0) (c : t_F'0) : ()
+    
+  
+  axiom unnest_trans'0_spec : forall self : t_F'0, b : t_F'0, c : t_F'0 . ([%#sops11] unnest'0 self b)
+   -> ([%#sops12] unnest'0 b c)  -> ([%#sops13] unnest'0 self c)
+  
+  function unnest_refl'0 [#"../../../creusot-contracts/src/std/ops.rs" 116 4 116 24] (self : t_F'0) : ()
+  
+  axiom unnest_refl'0_spec : forall self : t_F'0 . [%#sops10] unnest'0 self self
+  
+  function postcondition_mut_unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 111 4 111 85] (self : t_F'0) (args : t_Item'0) (res_state : t_F'0) (res : t_Option'0) : ()
+    
+  
+  axiom postcondition_mut_unnest'0_spec : forall self : t_F'0, args : t_Item'0, res_state : t_F'0, res : t_Option'0 . ([%#sops8] postcondition_mut'0 self args res_state res)
+   -> ([%#sops9] unnest'0 self res_state)
+  
+  predicate immutable'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 55 0 55 62] (f : t_F'0) =
+    [%#sfilter_map6] forall g : t_F'0 . unnest'0 f g  -> f = g
+  
+  predicate precise'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 62 0 62 61] (f1 : t_F'0) =
+    [%#sfilter_map7] forall f2 : t_F'0, i : t_Item'0 . not ((exists b : t_B'0 . postcondition_mut'0 f1 (i) f2 (C_Some'0 b))
+    /\ postcondition_mut'0 f1 (i) f2 (C_None'0))
+  
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_FilterMap'0)
+  
+  function func'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 23 4 23 22] (self : t_FilterMap'0) : t_F'0
+  
+  axiom func'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map3] inv'0 self  -> inv'1 (func'0 self)
+  
+  predicate invariant'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 31 4 31 30] (self : t_FilterMap'0) =
+    [%#sfilter_map2] no_precondition'0 (func'0 self) /\ immutable'0 (func'0 self) /\ precise'0 (func'0 self)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_FilterMap'0 [inv'0 x] . inv'0 x
+  = (invariant'0 x
+  /\ match x with
+    | {t_FilterMap__iter'0 = iter ; t_FilterMap__f'0 = f} -> inv'2 iter /\ inv'1 f
+    end)
+  
+  use seq.Seq
+  
+  use prelude.prelude.Int
+  
+  use map.Map
+  
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 16 4 16 22] (self : t_FilterMap'0) : t_I'0
+  
+  axiom iter'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map4] inv'0 self  -> inv'2 (iter'0 self)
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+    
+  
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+    
+  
+  axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter16] produces'1 a ab b)
+   -> ([%#siter17] produces'1 b bc c)  -> ([%#siter18] produces'1 a (Seq.(++) ab bc) c)
+  
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
+  
+  axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter15] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
+  
+  use seq.Seq
+  
+  use map.Map
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 83 4 83 67] (self : t_FilterMap'0) (visited : Seq.seq t_B'0) (succ : t_FilterMap'0)
+    
+   =
+    [%#sfilter_map1] invariant'0 self
+     -> unnest'0 (func'0 self) (func'0 succ)
+    /\ (exists s : Seq.seq t_Item'0, f : Map.map int int . produces'1 (iter'0 self) s (iter'0 succ)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> postcondition_mut'0 (func'0 self) (Seq.get s (Map.get f i)) (func'0 self) (C_Some'0 (Seq.get visited i)))
+    /\ (forall j : int . 0 <= j /\ j < Seq.length s
+     -> (not (exists i : int . 0 <= i /\ i < Seq.length visited /\ Map.get f i = j))
+    = postcondition_mut'0 (func'0 self) (Seq.get s j) (func'0 self) (C_None'0)))
+  
+  goal refines : [%#sfilter_map0] forall self : t_FilterMap'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq t_B'0) self
+   -> produces'0 self (Seq.empty  : Seq.seq t_B'0) self
+end
+module M_creusot_contracts__stdqy35z1__iter__filter_map__qyi13601925333174091585__produces_trans__refines [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 112 4 112 90] (* <std::iter::FilterMap<I, F> as std::iter::Iterator> *)
+  let%span sfilter_map0 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 112 4 112 90
+  let%span sfilter_map1 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 85 12 98 148
+  let%span sfilter_map2 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 34 12 38 32
+  let%span sfilter_map3 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 22 14 22 39
+  let%span sfilter_map4 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 15 14 15 39
+  let%span sfilter_map5 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 48 16 48 50
+  let%span sfilter_map6 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 56 16 56 52
+  let%span sfilter_map7 = "../../../creusot-contracts/src/std/iter/filter_map.rs" 63 16 63 135
+  let%span sops8 = "../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
+  let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 110 14 110 36
+  let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 115 14 115 31
+  let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 120 15 120 29
+  let%span sops12 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
+  let%span sops13 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
+  let%span sops14 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
+  
+  type t_I'0
+  
+  type t_F'0
+  
+  type t_FilterMap'0  =
+    { t_FilterMap__iter'0: t_I'0; t_FilterMap__f'0: t_F'0 }
+  
+  type t_B'0
+  
+  use seq.Seq
+  
+  predicate inv'2 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
+  
+  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_F'0)
+  
+  type t_Item'0
+  
+  predicate precondition'0 [#"../../../creusot-contracts/src/std/ops.rs" 77 4 77 45] (self : t_F'0) (args : t_Item'0)
+  
+  predicate no_precondition'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 47 0 47 68] (f : t_F'0) =
+    [%#sfilter_map5] forall i : t_Item'0 . precondition'0 f (i)
+  
+  type t_Option'0  =
+    | C_None'0
+    | C_Some'0 t_B'0
+  
+  predicate postcondition_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 85 4 85 73] (self : t_F'0) (args : t_Item'0) (result : t_Option'0)
     
   
+  use prelude.prelude.Borrow
+  
   predicate resolve'0 [#"../../../creusot-contracts/src/resolve.rs" 19 0 19 40] (_1 : t_F'0)
   
-  predicate postcondition_mut'0 [#"../../../creusot-contracts/src/std/ops.rs" 95 4 95 92] (self : t_F'0) (args : t_Item'0) (result_state : t_F'0) (result : bool)
+  predicate postcondition_mut'0 [#"../../../creusot-contracts/src/std/ops.rs" 95 4 95 92] (self : t_F'0) (args : t_Item'0) (result_state : t_F'0) (result : t_Option'0)
     
   
-  function fn_mut_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 129 4 129 55] (self : t_F'0) (args : t_Item'0) (res : bool) : ()
+  function fn_mut_once'0 [#"../../../creusot-contracts/src/std/ops.rs" 129 4 129 55] (self : t_F'0) (args : t_Item'0) (res : t_Option'0) : ()
     
   
-  axiom fn_mut_once'0_spec : forall self : t_F'0, args : t_Item'0, res : bool . [%#sops11] postcondition_once'0 self args res
+  axiom fn_mut_once'0_spec : forall self : t_F'0, args : t_Item'0, res : t_Option'0 . [%#sops14] postcondition_once'0 self args res
   = (exists res_state : t_F'0 . postcondition_mut'0 self args res_state res /\ resolve'0 res_state)
   
   predicate unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 103 4 103 36] (self : t_F'0) (_2 : t_F'0)
@@ -20876,65 +22874,67 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   function unnest_trans'0 [#"../../../creusot-contracts/src/std/ops.rs" 123 4 123 43] (self : t_F'0) (b : t_F'0) (c : t_F'0) : ()
     
   
-  axiom unnest_trans'0_spec : forall self : t_F'0, b : t_F'0, c : t_F'0 . ([%#sops8] unnest'0 self b)
-   -> ([%#sops9] unnest'0 b c)  -> ([%#sops10] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : t_F'0, b : t_F'0, c : t_F'0 . ([%#sops11] unnest'0 self b)
+   -> ([%#sops12] unnest'0 b c)  -> ([%#sops13] unnest'0 self c)
   
   function unnest_refl'0 [#"../../../creusot-contracts/src/std/ops.rs" 116 4 116 24] (self : t_F'0) : ()
   
-  axiom unnest_refl'0_spec : forall self : t_F'0 . [%#sops7] unnest'0 self self
+  axiom unnest_refl'0_spec : forall self : t_F'0 . [%#sops10] unnest'0 self self
   
-  function postcondition_mut_unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 111 4 111 85] (self : t_F'0) (args : t_Item'0) (res_state : t_F'0) (res : bool) : ()
+  function postcondition_mut_unnest'0 [#"../../../creusot-contracts/src/std/ops.rs" 111 4 111 85] (self : t_F'0) (args : t_Item'0) (res_state : t_F'0) (res : t_Option'0) : ()
     
   
-  axiom postcondition_mut_unnest'0_spec : forall self : t_F'0, args : t_Item'0, res_state : t_F'0, res : bool . ([%#sops5] postcondition_mut'0 self args res_state res)
-   -> ([%#sops6] unnest'0 self res_state)
+  axiom postcondition_mut_unnest'0_spec : forall self : t_F'0, args : t_Item'0, res_state : t_F'0, res : t_Option'0 . ([%#sops8] postcondition_mut'0 self args res_state res)
+   -> ([%#sops9] unnest'0 self res_state)
   
-  predicate invariant'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 31 4 31 30] (self : t_Filter'0) =
-    [%#sfilter2] forall f : t_F'0, i : t_Item'0 . precondition'0 f (i)
-    /\ (forall f : t_F'0, g : t_F'0 . unnest'0 f g  -> f = g)
-    /\ (forall f1 : t_F'0, f2 : t_F'0, i : t_Item'0 . not (postcondition_mut'0 f1 (i) f2 true
-    /\ postcondition_mut'0 f1 (i) f2 false))
+  predicate immutable'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 55 0 55 62] (f : t_F'0) =
+    [%#sfilter_map6] forall g : t_F'0 . unnest'0 f g  -> f = g
   
-  predicate inv'2 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
+  predicate precise'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 62 0 62 61] (f1 : t_F'0) =
+    [%#sfilter_map7] forall f2 : t_F'0, i : t_Item'0 . not ((exists b : t_B'0 . postcondition_mut'0 f1 (i) f2 (C_Some'0 b))
+    /\ postcondition_mut'0 f1 (i) f2 (C_None'0))
   
-  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_F'0)
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_FilterMap'0)
   
-  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Filter'0)
+  function func'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 23 4 23 22] (self : t_FilterMap'0) : t_F'0
   
-  axiom inv_axiom'0 [@rewrite] : forall x : t_Filter'0 [inv'0 x] . inv'0 x
+  axiom func'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map3] inv'0 self  -> inv'1 (func'0 self)
+  
+  predicate invariant'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 31 4 31 30] (self : t_FilterMap'0) =
+    [%#sfilter_map2] no_precondition'0 (func'0 self) /\ immutable'0 (func'0 self) /\ precise'0 (func'0 self)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_FilterMap'0 [inv'0 x] . inv'0 x
   = (invariant'0 x
   /\ match x with
-    | {t_Filter__iter'0 = iter ; t_Filter__predicate'0 = predicate'} -> inv'2 iter /\ inv'1 predicate'
+    | {t_FilterMap__iter'0 = iter ; t_FilterMap__f'0 = f} -> inv'2 iter /\ inv'1 f
     end)
   
-  function func'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 23 4 23 22] (self : t_Filter'0) : t_F'0
-  
-  axiom func'0_spec : forall self : t_Filter'0 . [%#sfilter3] inv'0 self  -> inv'1 (func'0 self)
+  use seq.Seq
   
   use prelude.prelude.Int
   
   use map.Map
   
-  function iter'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 16 4 16 22] (self : t_Filter'0) : t_I'0
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 16 4 16 22] (self : t_FilterMap'0) : t_I'0
   
-  axiom iter'0_spec : forall self : t_Filter'0 . [%#sfilter4] inv'0 self  -> inv'2 (iter'0 self)
+  axiom iter'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map4] inv'0 self  -> inv'2 (iter'0 self)
   
   use seq.Seq
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
-  axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter13] produces'1 a ab b)
-   -> ([%#siter14] produces'1 b bc c)  -> ([%#siter15] produces'1 a (Seq.(++) ab bc) c)
+  axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter16] produces'1 a ab b)
+   -> ([%#siter17] produces'1 b bc c)  -> ([%#siter18] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
-  axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter12] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
+  axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter15] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
   use seq.Seq
   
@@ -20942,20 +22942,27 @@ module M_creusot_contracts__stdqy35z1__iter__filter__qyi9573749579793237160__pro
   
   use seq.Seq
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/filter.rs" 85 4 85 67] (self : t_Filter'0) (visited : Seq.seq t_Item'0) (succ : t_Filter'0)
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/filter_map.rs" 83 4 83 67] (self : t_FilterMap'0) (visited : Seq.seq t_B'0) (succ : t_FilterMap'0)
     
    =
-    [%#sfilter1] invariant'0 self
+    [%#sfilter_map1] invariant'0 self
      -> unnest'0 (func'0 self) (func'0 succ)
     /\ (exists s : Seq.seq t_Item'0, f : Map.map int int . produces'1 (iter'0 self) s (iter'0 succ)
-    /\ (forall i : int, j : int . 0 <= i /\ i <= j /\ j < Seq.length visited
-     -> 0 <= Map.get f i /\ Map.get f i <= Map.get f j /\ Map.get f j < Seq.length s)
-    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> Seq.get visited i = Seq.get s (Map.get f i))
-    /\ (forall i : int . 0 <= i /\ i < Seq.length s
-     -> (exists j : int . 0 <= j /\ j < Seq.length visited /\ Map.get f j = i)
-    = postcondition_mut'0 (func'0 self) (Seq.get s i) (func'0 self) true))
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> postcondition_mut'0 (func'0 self) (Seq.get s (Map.get f i)) (func'0 self) (C_Some'0 (Seq.get visited i)))
+    /\ (forall j : int . 0 <= j /\ j < Seq.length s
+     -> (not (exists i : int . 0 <= i /\ i < Seq.length visited /\ Map.get f i = j))
+    = postcondition_mut'0 (func'0 self) (Seq.get s j) (func'0 self) (C_None'0)))
   
-  goal refines : [%#sfilter0] forall a : t_Filter'0 . forall ab : Seq.seq t_Item'0 . forall b : t_Filter'0 . forall bc : Seq.seq t_Item'0 . forall c : t_Filter'0 . produces'0 b bc c
+  use seq.Seq
+  
+  goal refines : [%#sfilter_map0] forall a : t_FilterMap'0 . forall ab : Seq.seq t_B'0 . forall b : t_FilterMap'0 . forall bc : Seq.seq t_B'0 . forall c : t_FilterMap'0 . produces'0 b bc c
   /\ produces'0 a ab b
    -> produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (Seq.(++) ab bc) c  -> produces'0 a (Seq.(++) ab bc) c)
@@ -20965,10 +22972,10 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi10730559947553418603__prod
   let%span sfuse1 = "../../../creusot-contracts/src/std/iter/fuse.rs" 29 12 35 13
   let%span sfuse2 = "../../../creusot-contracts/src/std/iter/fuse.rs" 8 14 8 39
   let%span sfuse3 = "../../../creusot-contracts/src/std/iter/fuse.rs" 9 14 9 71
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -21009,16 +23016,16 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi10730559947553418603__prod
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -21043,10 +23050,10 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi10730559947553418603__prod
   let%span sfuse1 = "../../../creusot-contracts/src/std/iter/fuse.rs" 29 12 35 13
   let%span sfuse2 = "../../../creusot-contracts/src/std/iter/fuse.rs" 8 14 8 39
   let%span sfuse3 = "../../../creusot-contracts/src/std/iter/fuse.rs" 9 14 9 71
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -21087,16 +23094,16 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi10730559947553418603__prod
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -21126,10 +23133,10 @@ module M_creusot_contracts__stdqy35z1__iter__map__qyi6597778842032428791__produc
   let%span sops8 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -21213,16 +23220,16 @@ module M_creusot_contracts__stdqy35z1__iter__map__qyi6597778842032428791__produc
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter12] produces'1 a ab b)
    -> ([%#siter13] produces'1 b bc c)  -> ([%#siter14] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter11] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -21269,10 +23276,10 @@ module M_creusot_contracts__stdqy35z1__iter__map__qyi6597778842032428791__produc
   let%span sops8 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -21354,16 +23361,16 @@ module M_creusot_contracts__stdqy35z1__iter__map__qyi6597778842032428791__produc
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter12] produces'1 a ab b)
    -> ([%#siter13] produces'1 b bc c)  -> ([%#siter14] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter11] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -21412,10 +23419,10 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi9026772487048432788__pr
   let%span sops6 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops7 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops8 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -21482,16 +23489,16 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi9026772487048432788__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter10] produces'1 a ab b)
    -> ([%#siter11] produces'1 b bc c)  -> ([%#siter12] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter9] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -21547,10 +23554,10 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi9026772487048432788__pr
   let%span sops6 = "../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops7 = "../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops8 = "../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter9 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter10 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter11 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -21615,16 +23622,16 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi9026772487048432788__pr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter10] produces'1 a ab b)
    -> ([%#siter11] produces'1 b bc c)  -> ([%#siter12] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter9] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -21820,11 +23827,11 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi16860283617022118777__pro
    -> produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (Seq.(++) ab bc) c  -> produces'0 a (Seq.(++) ab bc) c)
 end
-module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__produces_trans__refines [#"../../../creusot-contracts/src/std/iter/range.rs" 84 4 84 90] (* <std::ops::RangeInclusive<Idx> as std::iter::Iterator> *)
-  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 84 4 84 90
-  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 66 12 70 76
-  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
-  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
+module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__produces_trans__refines [#"../../../creusot-contracts/src/std/iter/range.rs" 110 4 110 90] (* <std::ops::RangeInclusive<Idx> as std::iter::Iterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 110 4 110 90
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 92 12 96 76
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
   let%span sops4 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
   
   type t_Idx'0
@@ -21849,7 +23856,7 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__pro
   axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops4] not is_empty_log'0 self
    -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
   
-  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 46 0 46 92] (r : t_RangeInclusive'0) : int
+  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92] (r : t_RangeInclusive'0) : int
     
    =
     [%#srange3] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
@@ -21859,7 +23866,7 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__pro
   
   use seq.Seq
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 64 4 64 64] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 90 4 90 64] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
     
    =
     [%#srange1] Seq.length visited = range_inclusive_len'0 self - range_inclusive_len'0 o
@@ -21875,11 +23882,11 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__pro
    -> produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (Seq.(++) ab bc) c  -> produces'0 a (Seq.(++) ab bc) c)
 end
-module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__produces_refl__refines [#"../../../creusot-contracts/src/std/iter/range.rs" 77 4 77 26] (* <std::ops::RangeInclusive<Idx> as std::iter::Iterator> *)
-  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 77 4 77 26
-  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 66 12 70 76
-  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
-  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
+module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__produces_refl__refines [#"../../../creusot-contracts/src/std/iter/range.rs" 103 4 103 26] (* <std::ops::RangeInclusive<Idx> as std::iter::Iterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 103 4 103 26
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 92 12 96 76
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
   let%span sops4 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
   
   type t_Idx'0
@@ -21906,7 +23913,7 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__pro
   axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops4] not is_empty_log'0 self
    -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
   
-  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 46 0 46 92] (r : t_RangeInclusive'0) : int
+  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92] (r : t_RangeInclusive'0) : int
     
    =
     [%#srange3] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
@@ -21916,7 +23923,7 @@ module M_creusot_contracts__stdqy35z1__iter__range__qyi11108913944999844411__pro
   
   use seq.Seq
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 64 4 64 64] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 90 4 90 64] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
     
    =
     [%#srange1] Seq.length visited = range_inclusive_len'0 self - range_inclusive_len'0 o
@@ -21988,15 +23995,129 @@ module M_creusot_contracts__stdqy35z1__iter__repeat__qyi8658929399712466629__pro
    -> produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (Seq.(++) ab bc) c  -> produces'0 a (Seq.(++) ab bc) c)
 end
+module M_creusot_contracts__stdqy35z1__iter__rev__qyi4378764544541057436__produces_refl__refines [#"../../../creusot-contracts/src/std/iter/rev.rs" 48 4 48 26] (* <std::iter::Rev<I> as std::iter::Iterator> *)
+  let%span srev0 = "../../../creusot-contracts/src/std/iter/rev.rs" 48 4 48 26
+  let%span srev1 = "../../../creusot-contracts/src/std/iter/rev.rs" 41 12 41 56
+  let%span srev2 = "../../../creusot-contracts/src/std/iter/rev.rs" 17 14 17 39
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 106 14 106 50
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 110 15 110 37
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 111 15 111 37
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 112 14 112 47
+  
+  type t_I'0
+  
+  type t_Rev'0  =
+    { t_Rev__iter'0: t_I'0 }
+  
+  use seq.Seq
+  
+  type t_Item'0
+  
+  use seq.Seq
+  
+  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
+  
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Rev'0)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_Rev'0 [inv'0 x] . inv'0 x
+  = match x with
+    | {t_Rev__iter'0 = iter} -> inv'1 iter
+    end
+  
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 18 4 18 22] (self : t_Rev'0) : t_I'0
+  
+  axiom iter'0_spec : forall self : t_Rev'0 . [%#srev2] inv'0 self  -> inv'1 (iter'0 self)
+  
+  use seq.Seq
+  
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter.rs" 103 4 103 70] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+    
+  
+  function produces_back_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 113 4 113 96] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+    
+  
+  axiom produces_back_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter4] produces_back'0 a ab b)
+   -> ([%#siter5] produces_back'0 b bc c)  -> ([%#siter6] produces_back'0 a (Seq.(++) ab bc) c)
+  
+  function produces_back_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 107 4 107 32] (self : t_I'0) : ()
+  
+  axiom produces_back_refl'0_spec : forall self : t_I'0 . [%#siter3] produces_back'0 self (Seq.empty  : Seq.seq t_Item'0) self
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 39 4 39 64] (self : t_Rev'0) (visited : Seq.seq t_Item'0) (o : t_Rev'0)
+    
+   =
+    [%#srev1] produces_back'0 (iter'0 self) visited (iter'0 o)
+  
+  goal refines : [%#srev0] forall self : t_Rev'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
+   -> produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
+end
+module M_creusot_contracts__stdqy35z1__iter__rev__qyi4378764544541057436__produces_trans__refines [#"../../../creusot-contracts/src/std/iter/rev.rs" 55 4 55 90] (* <std::iter::Rev<I> as std::iter::Iterator> *)
+  let%span srev0 = "../../../creusot-contracts/src/std/iter/rev.rs" 55 4 55 90
+  let%span srev1 = "../../../creusot-contracts/src/std/iter/rev.rs" 41 12 41 56
+  let%span srev2 = "../../../creusot-contracts/src/std/iter/rev.rs" 17 14 17 39
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 106 14 106 50
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 110 15 110 37
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 111 15 111 37
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 112 14 112 47
+  
+  type t_I'0
+  
+  type t_Rev'0  =
+    { t_Rev__iter'0: t_I'0 }
+  
+  type t_Item'0
+  
+  use seq.Seq
+  
+  predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_I'0)
+  
+  predicate inv'0 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_Rev'0)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_Rev'0 [inv'0 x] . inv'0 x
+  = match x with
+    | {t_Rev__iter'0 = iter} -> inv'1 iter
+    end
+  
+  function iter'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 18 4 18 22] (self : t_Rev'0) : t_I'0
+  
+  axiom iter'0_spec : forall self : t_Rev'0 . [%#srev2] inv'0 self  -> inv'1 (iter'0 self)
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter.rs" 103 4 103 70] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+    
+  
+  function produces_back_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 113 4 113 96] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+    
+  
+  axiom produces_back_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter4] produces_back'0 a ab b)
+   -> ([%#siter5] produces_back'0 b bc c)  -> ([%#siter6] produces_back'0 a (Seq.(++) ab bc) c)
+  
+  function produces_back_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 107 4 107 32] (self : t_I'0) : ()
+  
+  axiom produces_back_refl'0_spec : forall self : t_I'0 . [%#siter3] produces_back'0 self (Seq.empty  : Seq.seq t_Item'0) self
+  
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter/rev.rs" 39 4 39 64] (self : t_Rev'0) (visited : Seq.seq t_Item'0) (o : t_Rev'0)
+    
+   =
+    [%#srev1] produces_back'0 (iter'0 self) visited (iter'0 o)
+  
+  goal refines : [%#srev0] forall a : t_Rev'0 . forall ab : Seq.seq t_Item'0 . forall b : t_Rev'0 . forall bc : Seq.seq t_Item'0 . forall c : t_Rev'0 . produces'0 b bc c
+  /\ produces'0 a ab b
+   -> produces'0 b bc c
+  /\ produces'0 a ab b /\ (forall result : () . produces'0 a (Seq.(++) ab bc) c  -> produces'0 a (Seq.(++) ab bc) c)
+end
 module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produces_trans__refines [#"../../../creusot-contracts/src/std/iter/skip.rs" 81 4 81 90] (* <std::iter::Skip<I> as std::iter::Iterator> *)
   let%span sskip0 = "../../../creusot-contracts/src/std/iter/skip.rs" 81 4 81 90
   let%span sskip1 = "../../../creusot-contracts/src/std/iter/skip.rs" 62 12 67 74
   let%span sskip2 = "../../../creusot-contracts/src/std/iter/skip.rs" 21 14 21 50
   let%span sskip3 = "../../../creusot-contracts/src/std/iter/skip.rs" 14 14 14 39
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -22038,16 +24159,16 @@ module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produ
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -22077,10 +24198,10 @@ module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produ
   let%span sskip1 = "../../../creusot-contracts/src/std/iter/skip.rs" 62 12 67 74
   let%span sskip2 = "../../../creusot-contracts/src/std/iter/skip.rs" 21 14 21 50
   let%span sskip3 = "../../../creusot-contracts/src/std/iter/skip.rs" 14 14 14 39
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -22122,16 +24243,16 @@ module M_creusot_contracts__stdqy35z1__iter__skip__qyi3195031491774060502__produ
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -22159,10 +24280,10 @@ module M_creusot_contracts__stdqy35z1__iter__take__qyi12344256497067751022__prod
   let%span stake1 = "../../../creusot-contracts/src/std/iter/take.rs" 65 12 65 88
   let%span stake2 = "../../../creusot-contracts/src/std/iter/take.rs" 31 14 31 50
   let%span stake3 = "../../../creusot-contracts/src/std/iter/take.rs" 17 14 17 39
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -22204,16 +24325,16 @@ module M_creusot_contracts__stdqy35z1__iter__take__qyi12344256497067751022__prod
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -22230,10 +24351,10 @@ module M_creusot_contracts__stdqy35z1__iter__take__qyi12344256497067751022__prod
   let%span stake1 = "../../../creusot-contracts/src/std/iter/take.rs" 65 12 65 88
   let%span stake2 = "../../../creusot-contracts/src/std/iter/take.rs" 31 14 31 50
   let%span stake3 = "../../../creusot-contracts/src/std/iter/take.rs" 17 14 17 39
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
@@ -22275,16 +24396,16 @@ module M_creusot_contracts__stdqy35z1__iter__take__qyi12344256497067751022__prod
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -22303,10 +24424,10 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   let%span szip1 = "../../../creusot-contracts/src/std/iter/zip.rs" 46 12 49 95
   let%span szip2 = "../../../creusot-contracts/src/std/iter/zip.rs" 14 14 14 39
   let%span szip3 = "../../../creusot-contracts/src/std/iter/zip.rs" 21 14 21 39
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_A'0
   
@@ -22361,16 +24482,16 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_A'0) (visited : Seq.seq t_Item'0) (o : t_A'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_A'0) (visited : Seq.seq t_Item'0) (o : t_A'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_A'0) (ab : Seq.seq t_Item'0) (b : t_A'0) (bc : Seq.seq t_Item'0) (c : t_A'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_A'0) (ab : Seq.seq t_Item'0) (b : t_A'0) (bc : Seq.seq t_Item'0) (c : t_A'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_A'0, ab : Seq.seq t_Item'0, b : t_A'0, bc : Seq.seq t_Item'0, c : t_A'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_A'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_A'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_A'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -22382,16 +24503,16 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   
   use seq.Seq
   
-  predicate produces'2 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_B'0) (visited : Seq.seq t_Item'1) (o : t_B'0)
+  predicate produces'2 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_B'0) (visited : Seq.seq t_Item'1) (o : t_B'0)
     
   
-  function produces_trans'2 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_B'0) (ab : Seq.seq t_Item'1) (b : t_B'0) (bc : Seq.seq t_Item'1) (c : t_B'0) : ()
+  function produces_trans'2 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_B'0) (ab : Seq.seq t_Item'1) (b : t_B'0) (bc : Seq.seq t_Item'1) (c : t_B'0) : ()
     
   
   axiom produces_trans'2_spec : forall a : t_B'0, ab : Seq.seq t_Item'1, b : t_B'0, bc : Seq.seq t_Item'1, c : t_B'0 . ([%#siter5] produces'2 a ab b)
    -> ([%#siter6] produces'2 b bc c)  -> ([%#siter7] produces'2 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_B'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_B'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_B'0 . [%#siter4] produces'2 self (Seq.empty  : Seq.seq t_Item'1) self
   
@@ -22415,10 +24536,10 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   let%span szip1 = "../../../creusot-contracts/src/std/iter/zip.rs" 46 12 49 95
   let%span szip2 = "../../../creusot-contracts/src/std/iter/zip.rs" 14 14 14 39
   let%span szip3 = "../../../creusot-contracts/src/std/iter/zip.rs" 21 14 21 39
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter6 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter7 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_A'0
   
@@ -22475,16 +24596,16 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_A'0) (visited : Seq.seq t_Item'0) (o : t_A'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_A'0) (visited : Seq.seq t_Item'0) (o : t_A'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_A'0) (ab : Seq.seq t_Item'0) (b : t_A'0) (bc : Seq.seq t_Item'0) (c : t_A'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_A'0) (ab : Seq.seq t_Item'0) (b : t_A'0) (bc : Seq.seq t_Item'0) (c : t_A'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_A'0, ab : Seq.seq t_Item'0, b : t_A'0, bc : Seq.seq t_Item'0, c : t_A'0 . ([%#siter5] produces'1 a ab b)
    -> ([%#siter6] produces'1 b bc c)  -> ([%#siter7] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_A'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_A'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_A'0 . [%#siter4] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -22496,16 +24617,16 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   
   use seq.Seq
   
-  predicate produces'2 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_B'0) (visited : Seq.seq t_Item'1) (o : t_B'0)
+  predicate produces'2 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_B'0) (visited : Seq.seq t_Item'1) (o : t_B'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_B'0) (ab : Seq.seq t_Item'1) (b : t_B'0) (bc : Seq.seq t_Item'1) (c : t_B'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_B'0) (ab : Seq.seq t_Item'1) (b : t_B'0) (bc : Seq.seq t_Item'1) (c : t_B'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_B'0, ab : Seq.seq t_Item'1, b : t_B'0, bc : Seq.seq t_Item'1, c : t_B'0 . ([%#siter5] produces'2 a ab b)
    -> ([%#siter6] produces'2 b bc c)  -> ([%#siter7] produces'2 a (Seq.(++) ab bc) c)
   
-  function produces_refl'2 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_B'0) : ()
+  function produces_refl'2 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_B'0) : ()
   
   axiom produces_refl'2_spec : forall self : t_B'0 . [%#siter4] produces'2 self (Seq.empty  : Seq.seq t_Item'1) self
   
@@ -22520,13 +24641,13 @@ module M_creusot_contracts__stdqy35z1__iter__zip__qyi2281060687216883844__produc
   goal refines : [%#szip0] forall self : t_Zip'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq (t_Item'0, t_Item'1)) self
    -> produces'0 self (Seq.empty  : Seq.seq (t_Item'0, t_Item'1)) self
 end
-module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_refl__refines [#"../../../creusot-contracts/src/std/iter.rs" 223 4 223 26] (* <&mut I as std::iter::Iterator> *)
-  let%span siter0 = "../../../creusot-contracts/src/std/iter.rs" 223 4 223 26
-  let%span siter1 = "../../../creusot-contracts/src/std/iter.rs" 211 20 211 64
-  let%span siter2 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_refl__refines [#"../../../creusot-contracts/src/std/iter.rs" 279 4 279 26] (* <&mut I as std::iter::Iterator> *)
+  let%span siter0 = "../../../creusot-contracts/src/std/iter.rs" 279 4 279 26
+  let%span siter1 = "../../../creusot-contracts/src/std/iter.rs" 267 20 267 64
+  let%span siter2 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use prelude.prelude.Borrow
   
@@ -22540,20 +24661,20 @@ module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_re
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'0 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'0_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter3] produces'1 a ab b)
    -> ([%#siter4] produces'1 b bc c)  -> ([%#siter5] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter2] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 210 4 210 64] (self : borrowed t_I'0) (visited : Seq.seq t_Item'0) (o : borrowed t_I'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 266 4 266 64] (self : borrowed t_I'0) (visited : Seq.seq t_Item'0) (o : borrowed t_I'0)
     
    =
     [%#siter1] produces'1 self.current visited o.current /\ self.final = o.final
@@ -22561,13 +24682,13 @@ module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_re
   goal refines : [%#siter0] forall self : borrowed t_I'0 . forall result : () . produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
    -> produces'0 self (Seq.empty  : Seq.seq t_Item'0) self
 end
-module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_trans__refines [#"../../../creusot-contracts/src/std/iter.rs" 230 4 230 90] (* <&mut I as std::iter::Iterator> *)
-  let%span siter0 = "../../../creusot-contracts/src/std/iter.rs" 230 4 230 90
-  let%span siter1 = "../../../creusot-contracts/src/std/iter.rs" 211 20 211 64
-  let%span siter2 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_trans__refines [#"../../../creusot-contracts/src/std/iter.rs" 286 4 286 90] (* <&mut I as std::iter::Iterator> *)
+  let%span siter0 = "../../../creusot-contracts/src/std/iter.rs" 286 4 286 90
+  let%span siter1 = "../../../creusot-contracts/src/std/iter.rs" 267 20 267 64
+  let%span siter2 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter3 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter4 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter5 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use prelude.prelude.Borrow
   
@@ -22581,20 +24702,20 @@ module M_creusot_contracts__stdqy35z1__iter__qyi8355237225316942617__produces_tr
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter3] produces'1 a ab b)
    -> ([%#siter4] produces'1 b bc c)  -> ([%#siter5] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'0 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'0_spec : forall self : t_I'0 . [%#siter2] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
-  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 210 4 210 64] (self : borrowed t_I'0) (visited : Seq.seq t_Item'0) (o : borrowed t_I'0)
+  predicate produces'0 [#"../../../creusot-contracts/src/std/iter.rs" 266 4 266 64] (self : borrowed t_I'0) (visited : Seq.seq t_Item'0) (o : borrowed t_I'0)
     
    =
     [%#siter1] produces'1 self.current visited o.current /\ self.final = o.final
@@ -30047,10 +32168,10 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi7691061398646472980__is_fu
   let%span sfuse9 = "../../../creusot-contracts/src/std/iter/fuse.rs" 8 14 8 39
   let%span sfuse10 = "../../../creusot-contracts/src/std/iter/fuse.rs" 9 14 9 71
   let%span smodel11 = "../../../creusot-contracts/src/model.rs" 110 8 110 22
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   use prelude.prelude.Borrow
   
@@ -30093,16 +32214,16 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi7691061398646472980__is_fu
   axiom view'0_spec : forall self : t_Fuse'0 . ([%#sfuse9] inv'0 self  -> inv'1 (view'0 self))
   && ([%#sfuse10] forall other : t_Fuse'0 . view'0 self = view'0 other  -> self = other)
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter13] produces'1 a ab b)
    -> ([%#siter14] produces'1 b bc c)  -> ([%#siter15] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter12] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
@@ -30133,7 +32254,7 @@ module M_creusot_contracts__stdqy35z1__iter__fuse__qyi7691061398646472980__is_fu
   function view'1 [#"../../../creusot-contracts/src/model.rs" 109 4 109 33] (self : borrowed (t_Fuse'0)) : t_Option'0 =
     [%#smodel11] view'0 self.current
   
-  predicate completed'1 [#"../../../creusot-contracts/src/std/iter.rs" 35 4 35 36] (self : borrowed t_I'0)
+  predicate completed'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 36] (self : borrowed t_I'0)
   
   predicate completed'0 [#"../../../creusot-contracts/src/std/iter/fuse.rs" 18 4 18 35] (self : borrowed (t_Fuse'0)) =
     [%#sfuse2] (view'1 self = C_None'0
@@ -30160,10 +32281,10 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4413682431414748756__ne
   let%span smap_inv9 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 30 14 30 42
   let%span smap_inv10 = "../../../creusot-contracts/src/std/iter/map_inv.rs" 26 4 26 10
   let%span sinvariant11 = "../../../creusot-contracts/src/invariant.rs" 34 20 34 44
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter13 = "../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter15 = "../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span sops16 = "../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
   let%span sops17 = "../../../creusot-contracts/src/std/ops.rs" 110 14 110 36
   let%span sops18 = "../../../creusot-contracts/src/std/ops.rs" 115 14 115 31
@@ -30197,20 +32318,20 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4413682431414748756__ne
   
   use seq.Seq
   
-  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 32 4 32 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
+  predicate produces'1 [#"../../../creusot-contracts/src/std/iter.rs" 36 4 36 65] (self : t_I'0) (visited : Seq.seq t_Item'0) (o : t_I'0)
     
   
-  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 45 4 45 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
+  function produces_trans'1 [#"../../../creusot-contracts/src/std/iter.rs" 49 4 49 91] (a : t_I'0) (ab : Seq.seq t_Item'0) (b : t_I'0) (bc : Seq.seq t_Item'0) (c : t_I'0) : ()
     
   
   axiom produces_trans'1_spec : forall a : t_I'0, ab : Seq.seq t_Item'0, b : t_I'0, bc : Seq.seq t_Item'0, c : t_I'0 . ([%#siter13] produces'1 a ab b)
    -> ([%#siter14] produces'1 b bc c)  -> ([%#siter15] produces'1 a (Seq.(++) ab bc) c)
   
-  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 27] (self : t_I'0) : ()
+  function produces_refl'1 [#"../../../creusot-contracts/src/std/iter.rs" 43 4 43 27] (self : t_I'0) : ()
   
   axiom produces_refl'1_spec : forall self : t_I'0 . [%#siter12] produces'1 self (Seq.empty  : Seq.seq t_Item'0) self
   
-  predicate completed'1 [#"../../../creusot-contracts/src/std/iter.rs" 35 4 35 36] (self : borrowed t_I'0)
+  predicate completed'1 [#"../../../creusot-contracts/src/std/iter.rs" 39 4 39 36] (self : borrowed t_I'0)
   
   use seq.Seq
   
@@ -30420,6 +32541,186 @@ module M_creusot_contracts__stdqy35z1__iter__map_inv__qyi4413682431414748756__ne
     end
   /\ inv'1 result)
 end
+module M_creusot_contracts__stdqy35z1__iter__range__qyi16137414346896623968__produces_back_refl__refines [#"../../../creusot-contracts/src/std/iter/range.rs" 59 4 59 31] (* <std::ops::Range<Idx> as std::iter::DoubleEndedIterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 59 4 59 31
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 48 12 52 68
+  
+  type t_Idx'0
+  
+  type t_Range'0  =
+    { t_Range__start'0: t_Idx'0; t_Range__end'0: t_Idx'0 }
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use prelude.prelude.Int
+  
+  function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 46 4 46 69] (self : t_Range'0) (visited : Seq.seq t_Idx'0) (o : t_Range'0)
+    
+   =
+    [%#srange1] self.t_Range__start'0 = o.t_Range__start'0
+    /\ deep_model'0 self.t_Range__end'0 >= deep_model'0 o.t_Range__end'0
+    /\ (Seq.length visited > 0  -> deep_model'0 o.t_Range__end'0 >= deep_model'0 o.t_Range__start'0)
+    /\ Seq.length visited = deep_model'0 o.t_Range__end'0 - deep_model'0 self.t_Range__end'0
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> deep_model'0 (Seq.get visited i) = deep_model'0 self.t_Range__end'0 - i)
+  
+  goal refines : [%#srange0] forall self : t_Range'0 . forall result : () . produces_back'0 self (Seq.empty  : Seq.seq t_Idx'0) self
+   -> produces_back'0 self (Seq.empty  : Seq.seq t_Idx'0) self
+end
+module M_creusot_contracts__stdqy35z1__iter__range__qyi16137414346896623968__produces_back_trans__refines [#"../../../creusot-contracts/src/std/iter/range.rs" 66 4 66 95] (* <std::ops::Range<Idx> as std::iter::DoubleEndedIterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 66 4 66 95
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 48 12 52 68
+  
+  type t_Idx'0
+  
+  type t_Range'0  =
+    { t_Range__start'0: t_Idx'0; t_Range__end'0: t_Idx'0 }
+  
+  use seq.Seq
+  
+  use prelude.prelude.Int
+  
+  function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 46 4 46 69] (self : t_Range'0) (visited : Seq.seq t_Idx'0) (o : t_Range'0)
+    
+   =
+    [%#srange1] self.t_Range__start'0 = o.t_Range__start'0
+    /\ deep_model'0 self.t_Range__end'0 >= deep_model'0 o.t_Range__end'0
+    /\ (Seq.length visited > 0  -> deep_model'0 o.t_Range__end'0 >= deep_model'0 o.t_Range__start'0)
+    /\ Seq.length visited = deep_model'0 o.t_Range__end'0 - deep_model'0 self.t_Range__end'0
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> deep_model'0 (Seq.get visited i) = deep_model'0 self.t_Range__end'0 - i)
+  
+  use seq.Seq
+  
+  goal refines : [%#srange0] forall a : t_Range'0 . forall ab : Seq.seq t_Idx'0 . forall b : t_Range'0 . forall bc : Seq.seq t_Idx'0 . forall c : t_Range'0 . produces_back'0 b bc c
+  /\ produces_back'0 a ab b
+   -> produces_back'0 b bc c
+  /\ produces_back'0 a ab b
+  /\ (forall result : () . produces_back'0 a (Seq.(++) ab bc) c  -> produces_back'0 a (Seq.(++) ab bc) c)
+end
+module M_creusot_contracts__stdqy35z1__iter__range__qyi12106466433038921999__produces_back_refl__refines [#"../../../creusot-contracts/src/std/iter/range.rs" 129 4 129 31] (* <std::ops::RangeInclusive<Idx> as std::iter::DoubleEndedIterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 129 4 129 31
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 118 12 122 74
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
+  let%span sops4 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
+  
+  type t_Idx'0
+  
+  type t_RangeInclusive'0  =
+    { t_RangeInclusive__start'0: t_Idx'0; t_RangeInclusive__end'0: t_Idx'0; t_RangeInclusive__exhausted'0: bool }
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  function start_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 193 4 193 29] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  use prelude.prelude.Int
+  
+  function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
+  
+  function end_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 199 4 199 27] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  function is_empty_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 206 4 209 35] (self : t_RangeInclusive'0) : bool
+  
+  axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops4] not is_empty_log'0 self
+   -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
+  
+  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92] (r : t_RangeInclusive'0) : int
+    
+   =
+    [%#srange3] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
+  
+  axiom range_inclusive_len'0_spec : forall r : t_RangeInclusive'0 . [%#srange2] is_empty_log'0 r
+  = (range_inclusive_len'0 r = 0)
+  
+  use seq.Seq
+  
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 116 4 116 69] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
+    
+   =
+    [%#srange1] Seq.length visited = range_inclusive_len'0 self - range_inclusive_len'0 o
+    /\ (is_empty_log'0 self  -> is_empty_log'0 o)
+    /\ (is_empty_log'0 o \/ start_log'0 self = start_log'0 o)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> deep_model'0 (Seq.get visited i) = deep_model'0 (end_log'0 self) - i)
+  
+  goal refines : [%#srange0] forall self : t_RangeInclusive'0 . forall result : () . produces_back'0 self (Seq.empty  : Seq.seq t_Idx'0) self
+   -> produces_back'0 self (Seq.empty  : Seq.seq t_Idx'0) self
+end
+module M_creusot_contracts__stdqy35z1__iter__range__qyi12106466433038921999__produces_back_trans__refines [#"../../../creusot-contracts/src/std/iter/range.rs" 136 4 136 95] (* <std::ops::RangeInclusive<Idx> as std::iter::DoubleEndedIterator> *)
+  let%span srange0 = "../../../creusot-contracts/src/std/iter/range.rs" 136 4 136 95
+  let%span srange1 = "../../../creusot-contracts/src/std/iter/range.rs" 118 12 122 74
+  let%span srange2 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange3 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
+  let%span sops4 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
+  
+  type t_Idx'0
+  
+  type t_RangeInclusive'0  =
+    { t_RangeInclusive__start'0: t_Idx'0; t_RangeInclusive__end'0: t_Idx'0; t_RangeInclusive__exhausted'0: bool }
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  function start_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 193 4 193 29] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  use prelude.prelude.Int
+  
+  function deep_model'0 [#"../../../creusot-contracts/src/model.rs" 29 4 29 45] (self : t_Idx'0) : int
+  
+  function end_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 199 4 199 27] (self : t_RangeInclusive'0) : t_Idx'0
+  
+  function is_empty_log'0 [#"../../../creusot-contracts/src/std/ops.rs" 206 4 209 35] (self : t_RangeInclusive'0) : bool
+  
+  axiom is_empty_log'0_spec : forall self : t_RangeInclusive'0 . [%#sops4] not is_empty_log'0 self
+   -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self)
+  
+  function range_inclusive_len'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 72 0 72 92] (r : t_RangeInclusive'0) : int
+    
+   =
+    [%#srange3] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
+  
+  axiom range_inclusive_len'0_spec : forall r : t_RangeInclusive'0 . [%#srange2] is_empty_log'0 r
+  = (range_inclusive_len'0 r = 0)
+  
+  use seq.Seq
+  
+  predicate produces_back'0 [#"../../../creusot-contracts/src/std/iter/range.rs" 116 4 116 69] (self : t_RangeInclusive'0) (visited : Seq.seq t_Idx'0) (o : t_RangeInclusive'0)
+    
+   =
+    [%#srange1] Seq.length visited = range_inclusive_len'0 self - range_inclusive_len'0 o
+    /\ (is_empty_log'0 self  -> is_empty_log'0 o)
+    /\ (is_empty_log'0 o \/ start_log'0 self = start_log'0 o)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> deep_model'0 (Seq.get visited i) = deep_model'0 (end_log'0 self) - i)
+  
+  use seq.Seq
+  
+  goal refines : [%#srange0] forall a : t_RangeInclusive'0 . forall ab : Seq.seq t_Idx'0 . forall b : t_RangeInclusive'0 . forall bc : Seq.seq t_Idx'0 . forall c : t_RangeInclusive'0 . produces_back'0 b bc c
+  /\ produces_back'0 a ab b
+   -> produces_back'0 b bc c
+  /\ produces_back'0 a ab b
+  /\ (forall result : () . produces_back'0 a (Seq.(++) ab bc) c  -> produces_back'0 a (Seq.(++) ab bc) c)
+end
 module M_creusot_contracts__stdqy35z1__ops__qyi14194840286170235833__unnest_trans__refines [#"../../../creusot-contracts/src/std/ops.rs" 123 4 123 43] (* <F as std::ops::FnMutExt<Args>> *)
   let%span sops0 = "../../../creusot-contracts/src/std/ops.rs" 123 4 123 43
   
@@ -30667,10 +32968,10 @@ module M_creusot_contracts__logic__fmap__qyi4648834920430559677__clone__refines
   goal refines : [%#sfmap0] forall self : t_FMap'0 . inv'0 self
    -> inv'0 self /\ (forall result : t_FMap'0 . result = self /\ inv'1 result  -> result = self /\ inv'1 result)
 end
-module M_creusot_contracts__logic__fset__qyi11096226875104347554__clone__refines [#"../../../creusot-contracts/src/logic/fset.rs" 323 4 323 27] (* <logic::fset::FSet<T> as std::clone::Clone> *)
-  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 323 4 323 27
+module M_creusot_contracts__logic__fset__qyi11096226875104347554__clone__refines [#"../../../creusot-contracts/src/logic/fset.rs" 443 4 443 27] (* <logic::fset::FSet<T> as std::clone::Clone> *)
+  let%span sfset0 = "../../../creusot-contracts/src/logic/fset.rs" 443 4 443 27
   let%span sinvariant1 = "../../../creusot-contracts/src/invariant.rs" 24 8 24 18
-  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 337 20 337 63
+  let%span sfset2 = "../../../creusot-contracts/src/logic/fset.rs" 457 20 457 63
   let%span sfset3 = "../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   
   use prelude.prelude.Borrow
@@ -30688,7 +32989,7 @@ module M_creusot_contracts__logic__fset__qyi11096226875104347554__clone__refines
   
   predicate inv'2 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : t_T'0)
   
-  predicate invariant'1 [#"../../../creusot-contracts/src/logic/fset.rs" 336 4 336 30] (self : Fset.fset t_T'0) =
+  predicate invariant'1 [#"../../../creusot-contracts/src/logic/fset.rs" 456 4 456 30] (self : Fset.fset t_T'0) =
     [%#sfset2] forall x : t_T'0 . contains'0 self x  -> inv'2 x
   
   predicate inv'1 [#"../../../creusot-contracts/src/invariant.rs" 41 0 41 35] (_1 : Fset.fset t_T'0)
diff --git a/creusot/tests/creusot-contracts/creusot-contracts/why3session.xml b/creusot/tests/creusot-contracts/creusot-contracts/why3session.xml
index 7303c86f6..342324306 100644
--- a/creusot/tests/creusot-contracts/creusot-contracts/why3session.xml
+++ b/creusot/tests/creusot-contracts/creusot-contracts/why3session.xml
@@ -72,13 +72,13 @@
    <proof prover="3" timelimit="5"><result status="valid" time="0.101945" steps="24"/></proof>
    </goal>
    <goal name="vc_produces_trans&#39;0.0.5" proved="true">
-   <proof prover="3" timelimit="5"><result status="valid" time="0.157090" steps="307"/></proof>
+   <proof prover="3" timelimit="5"><result status="valid" time="0.040976" steps="307"/></proof>
    </goal>
    <goal name="vc_produces_trans&#39;0.0.6" proved="true">
-   <proof prover="2"><result status="valid" time="0.769344" steps="57017"/></proof>
+   <proof prover="2"><result status="valid" time="0.228992" steps="57017"/></proof>
    </goal>
    <goal name="vc_produces_trans&#39;0.0.7" proved="true">
-   <proof prover="2"><result status="valid" time="0.192636" steps="12621"/></proof>
+   <proof prover="2"><result status="valid" time="0.067490" steps="12621"/></proof>
    </goal>
   </transf>
   </goal>
@@ -124,7 +124,7 @@
    <proof prover="3" timelimit="5"><result status="valid" time="0.147017" steps="285"/></proof>
    </goal>
    <goal name="vc_produces_trans&#39;0.0.6" proved="true">
-   <proof prover="2"><result status="valid" time="0.838220" steps="55888"/></proof>
+   <proof prover="2"><result status="valid" time="0.255138" steps="55888"/></proof>
    </goal>
    <goal name="vc_produces_trans&#39;0.0.7" proved="true">
    <proof prover="0"><result status="valid" time="0.088170" steps="39324"/></proof>
@@ -173,7 +173,7 @@
    <proof prover="3" timelimit="5"><result status="valid" time="0.101992" steps="285"/></proof>
    </goal>
    <goal name="vc_produces_trans&#39;0.0.6" proved="true">
-   <proof prover="2"><result status="valid" time="0.769145" steps="56601"/></proof>
+   <proof prover="2"><result status="valid" time="0.270463" steps="56601"/></proof>
    </goal>
    <goal name="vc_produces_trans&#39;0.0.7" proved="true">
    <proof prover="2"><result status="valid" time="0.158387" steps="11854"/></proof>
@@ -243,7 +243,7 @@
    <proof prover="3" timelimit="5"><result status="valid" time="0.069091" steps="55"/></proof>
    </goal>
    <goal name="vc_set_produces_trans&#39;0.0.8" proved="true">
-   <proof prover="1"><result status="valid" time="0.205048" steps="22863"/></proof>
+   <proof prover="1"><result status="valid" time="0.068336" steps="22863"/></proof>
    </goal>
   </transf>
   </goal>
@@ -310,11 +310,131 @@
  <proof prover="2"><result status="valid" time="0.033142" steps="5804"/></proof>
  </goal>
 </theory>
+<theory name="M_creusot_contracts__logic__fset__qyi12147533290214288165__ext_eq" proved="true">
+ <goal name="vc_ext_eq&#39;0" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.021474" steps="7"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__qyi12147533290214288165__singleton" proved="true">
+ <goal name="vc_singleton&#39;0" proved="true">
+ <proof prover="2"><result status="valid" time="0.026037" steps="5898"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__qyi12147533290214288165__unions" proved="true">
+ <goal name="vc_unions&#39;0" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.048969" steps="288"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__qyi12147533290214288165__replicate" proved="true">
+ <goal name="vc_replicate&#39;0" proved="true">
+ <transf name="split_vc" proved="true" >
+  <goal name="vc_replicate&#39;0.0" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.018137" steps="18"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.1" proved="true">
+  <proof prover="2"><result status="valid" time="0.035926" steps="8058"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.2" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.037759" steps="23"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.3" proved="true">
+  <proof prover="0"><result status="valid" time="0.025330" steps="81688"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.4" proved="true">
+  <proof prover="2"><result status="valid" time="0.053614" steps="7117"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.5" expl="replicate requires" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.027284" steps="4"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.6" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.024481" steps="4"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.7" proved="true">
+  <proof prover="1"><result status="valid" time="0.057780" steps="9408"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.8" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.020809" steps="34"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.9" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.045966" steps="144"/></proof>
+  </goal>
+  <goal name="vc_replicate&#39;0.10" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.047232" steps="221"/></proof>
+  </goal>
+ </transf>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__qyi12147533290214288165__replicate_up_to" proved="true">
+ <goal name="vc_replicate_up_to&#39;0" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.055708" steps="349"/></proof>
+ </goal>
+</theory>
 <theory name="M_creusot_contracts__logic__fset__qyi11096226875104347554__clone__refines" proved="true">
  <goal name="refines" proved="true">
  <proof prover="3"><result status="valid" time="0.032160" steps="0"/></proof>
  </goal>
 </theory>
+<theory name="M_creusot_contracts__logic__fset__unions_union" proved="true">
+ <goal name="vc_unions_union&#39;0" proved="true">
+ <proof prover="0"><result status="valid" time="1.115624" steps="2240462"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__map_union" proved="true">
+ <goal name="vc_map_union&#39;0" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.044750" steps="357"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__concat_union" proved="true">
+ <goal name="vc_concat_union&#39;0" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.125805" steps="839"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__cons_concat" proved="true">
+ <goal name="vc_cons_concat&#39;0" proved="true">
+ <transf name="split_vc" proved="true" >
+  <goal name="vc_cons_concat&#39;0.0" proved="true">
+  <proof prover="0"><result status="valid" time="0.000001" steps="57091"/></proof>
+  </goal>
+  <goal name="vc_cons_concat&#39;0.1" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.020572" steps="80"/></proof>
+  </goal>
+  <goal name="vc_cons_concat&#39;0.2" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.022460" steps="105"/></proof>
+  </goal>
+  <goal name="vc_cons_concat&#39;0.3" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.040282" steps="242"/></proof>
+  </goal>
+ </transf>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__concat_replicate" proved="true">
+ <goal name="vc_concat_replicate&#39;0" proved="true">
+ <proof prover="2"><result status="valid" time="0.177275" steps="27508"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__concat_empty" proved="true">
+ <goal name="vc_concat_empty&#39;0" proved="true">
+ <transf name="split_vc" proved="true" >
+  <goal name="vc_concat_empty&#39;0.0" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.017356" steps="29"/></proof>
+  </goal>
+  <goal name="vc_concat_empty&#39;0.1" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.029237" steps="31"/></proof>
+  </goal>
+  <goal name="vc_concat_empty&#39;0.2" proved="true">
+  <proof prover="3" timelimit="5"><result status="valid" time="0.198766" steps="1674"/></proof>
+  </goal>
+  <goal name="vc_concat_empty&#39;0.3" proved="true">
+  <proof prover="2"><result status="valid" time="0.550099" steps="106183"/></proof>
+  </goal>
+ </transf>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__logic__fset__concat_replicate_up_to" proved="true">
+ <goal name="vc_concat_replicate_up_to&#39;0" proved="true">
+ <proof prover="1"><result status="valid" time="0.074340" steps="30160"/></proof>
+ </goal>
+</theory>
 <theory name="M_creusot_contracts__stdqy35z1__cmp__extern_spec_std_cmp_PartialEq_Rhs_ne_body" proved="true">
  <goal name="vc_extern_spec_std_cmp_PartialEq_Rhs_ne_body&#39;0" proved="true">
  <proof prover="3"><result status="valid" time="0.016119" steps="22"/></proof>
@@ -2266,7 +2386,7 @@
     <proof prover="3"><result status="valid" time="0.019201" steps="4"/></proof>
     </goal>
     <goal name="vc_produces_refl&#39;0.0.0.1" proved="true">
-    <proof prover="0" timelimit="1"><result status="valid" time="0.113877" steps="30652"/></proof>
+    <proof prover="0" timelimit="1"><result status="valid" time="0.113877" steps="30627"/></proof>
     </goal>
    </transf>
    </goal>
@@ -2286,7 +2406,7 @@
   <goal name="vc_produces_trans&#39;0.0" proved="true">
   <transf name="split_vc" proved="true" >
    <goal name="vc_produces_trans&#39;0.0.0" proved="true">
-   <proof prover="3"><result status="valid" time="0.018270" steps="28"/></proof>
+   <proof prover="3"><result status="valid" time="0.018270" steps="31"/></proof>
    </goal>
    <goal name="vc_produces_trans&#39;0.0.1" proved="true">
    <transf name="destruct_rec" proved="true" arg1="H3">
@@ -2308,34 +2428,34 @@
         <proof prover="3"><result status="valid" time="0.011349" steps="11"/></proof>
         </goal>
         <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.1" proved="true">
-        <proof prover="3"><result status="valid" time="0.364186" steps="1950"/></proof>
+        <proof prover="3"><result status="valid" time="0.013356" steps="60"/></proof>
         </goal>
         <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.2" proved="true">
-        <proof prover="3"><result status="valid" time="0.232402" steps="2445"/></proof>
+        <proof prover="3"><result status="valid" time="0.024150" steps="76"/></proof>
         </goal>
         <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.3" proved="true">
-        <proof prover="3"><result status="valid" time="0.442625" steps="2591"/></proof>
+        <proof prover="3"><result status="valid" time="0.016550" steps="133"/></proof>
         </goal>
         <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.4" proved="true">
-        <proof prover="2" timelimit="1"><result status="valid" time="0.057569" steps="9418"/></proof>
+        <proof prover="2" timelimit="1"><result status="valid" time="0.057569" steps="9699"/></proof>
         </goal>
         <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.5" proved="true">
-        <proof prover="2" timelimit="1"><result status="valid" time="0.056024" steps="8897"/></proof>
+        <proof prover="2" timelimit="1"><result status="valid" time="0.056024" steps="9044"/></proof>
         </goal>
         <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.6" proved="true">
         <transf name="case" proved="true" arg1="(i&lt;length s)">
          <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.6.0" expl="true case" proved="true">
-         <proof prover="3"><result status="valid" time="0.062073" steps="112"/></proof>
+         <proof prover="3"><result status="valid" time="0.062073" steps="114"/></proof>
          </goal>
          <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.6.1" expl="false case" proved="true">
-         <transf name="instantiate" proved="true" arg1="H9" arg2="(i-length s)">
+         <transf name="instantiate" proved="true" arg1="H10" arg2="(i - length s)">
           <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.6.1.0" expl="false case" proved="true">
           <transf name="replace" proved="true" arg1="(func&#39;0 b)" arg2="(func&#39;0 a)" arg3="in" arg4="Hinst">
            <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.6.1.0.0" expl="false case" proved="true">
-           <proof prover="3"><result status="valid" time="0.160334" steps="482"/></proof>
+           <proof prover="3" timelimit="5"><result status="valid" time="0.042261" steps="403"/></proof>
            </goal>
            <goal name="vc_produces_trans&#39;0.0.1.1.1.0.0.6.1.0.1" expl="equality hypothesis" proved="true">
-           <proof prover="2" timelimit="1"><result status="valid" time="0.090160" steps="4412"/></proof>
+           <proof prover="2"><result status="valid" time="0.023250" steps="4516"/></proof>
            </goal>
           </transf>
           </goal>
@@ -2388,6 +2508,124 @@
  <proof prover="3"><result status="valid" time="0.016216" steps="0"/></proof>
  </goal>
 </theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__filter_map__qyi13601925333174091585__produces_refl__refines" proved="true">
+ <goal name="refines" proved="true">
+ <proof prover="0"><result status="valid" time="0.013757" steps="985"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__filter_map__qyi13601925333174091585__produces_refl" proved="true">
+ <goal name="vc_produces_refl&#39;0" proved="true">
+ <transf name="inline_goal" proved="true" >
+  <goal name="vc_produces_refl&#39;0.0" proved="true">
+  <transf name="split_vc" proved="true" >
+   <goal name="vc_produces_refl&#39;0.0.0" proved="true">
+   <proof prover="3" timelimit="5"><result status="valid" time="0.015181" steps="6"/></proof>
+   </goal>
+   <goal name="vc_produces_refl&#39;0.0.1" proved="true">
+   <transf name="exists" proved="true" arg1="(empty: seq t_Item&#39;0)">
+    <goal name="vc_produces_refl&#39;0.0.1.0" proved="true">
+    <transf name="exists" proved="true" arg1="(fun (i: int) -&gt; i)">
+     <goal name="vc_produces_refl&#39;0.0.1.0.0" proved="true">
+     <proof prover="1"><result status="valid" time="0.015957" steps="7793"/></proof>
+     </goal>
+    </transf>
+    </goal>
+   </transf>
+   </goal>
+  </transf>
+  </goal>
+ </transf>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__filter_map__qyi13601925333174091585__produces_trans__refines" proved="true">
+ <goal name="refines" proved="true">
+ <proof prover="0"><result status="valid" time="0.013384" steps="985"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__filter_map__qyi13601925333174091585__produces_trans" proved="true">
+ <goal name="vc_produces_trans&#39;0" proved="true">
+ <transf name="split_vc" proved="true" >
+  <goal name="vc_produces_trans&#39;0.0" proved="true">
+  <transf name="unfold" proved="true" arg1="produces&#39;0" arg2="in" arg3="H,H1">
+   <goal name="vc_produces_trans&#39;0.0.0" proved="true">
+   <transf name="inline_goal" proved="true" >
+    <goal name="vc_produces_trans&#39;0.0.0.0" proved="true">
+    <transf name="split_vc" proved="true" >
+     <goal name="vc_produces_trans&#39;0.0.0.0.0" proved="true">
+     <proof prover="2"><result status="valid" time="0.029754" steps="6301"/></proof>
+     </goal>
+     <goal name="vc_produces_trans&#39;0.0.0.0.1" proved="true">
+     <transf name="destruct" proved="true" arg1="H1">
+      <goal name="vc_produces_trans&#39;0.0.0.0.1.0" expl="destruct premise" proved="true">
+      <proof prover="0"><result status="valid" time="0.014334" steps="2792"/></proof>
+      </goal>
+      <goal name="vc_produces_trans&#39;0.0.0.0.1.1" proved="true">
+      <transf name="destruct" proved="true" arg1="H1">
+       <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0" proved="true">
+       <transf name="destruct" proved="true" arg1="H1">
+        <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0" proved="true">
+        <transf name="destruct" proved="true" arg1="H3">
+         <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.0" expl="destruct premise" proved="true">
+         <proof prover="2"><result status="valid" time="0.039033" steps="5460"/></proof>
+         </goal>
+         <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1" proved="true">
+         <transf name="destruct" proved="true" arg1="H3">
+          <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0" proved="true">
+          <transf name="destruct" proved="true" arg1="H3">
+           <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0" proved="true">
+           <transf name="exists" proved="true" arg1="(s ++ s1)">
+            <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0.0" proved="true">
+            <transf name="exists" proved="true" arg1="(fun i -&gt; if i &lt; length ab then f i else f1 (i - length ab) + length s)">
+             <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0.0.0" proved="true">
+             <transf name="split_vc" proved="true" >
+              <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0.0.0.0" proved="true">
+              <proof prover="1"><result status="valid" time="0.024923" steps="8170"/></proof>
+              </goal>
+              <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0.0.0.1" proved="true">
+              <proof prover="1"><result status="valid" time="0.050514" steps="10612"/></proof>
+              </goal>
+              <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0.0.0.2" proved="true">
+              <proof prover="0"><result status="valid" time="0.026849" steps="35647"/></proof>
+              </goal>
+              <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0.0.0.3" proved="true">
+              <proof prover="0"><result status="valid" time="0.024728" steps="37561"/></proof>
+              </goal>
+              <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0.0.0.4" proved="true">
+              <proof prover="0"><result status="valid" time="0.018399" steps="37122"/></proof>
+              </goal>
+              <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0.0.0.5" proved="true">
+              <proof prover="3" timelimit="5"><result status="valid" time="0.066458" steps="402"/></proof>
+              </goal>
+              <goal name="vc_produces_trans&#39;0.0.0.0.1.1.0.0.1.0.0.0.0.6" proved="true">
+              <proof prover="0"><result status="valid" time="0.029189" steps="39869"/></proof>
+              </goal>
+             </transf>
+             </goal>
+            </transf>
+            </goal>
+           </transf>
+           </goal>
+          </transf>
+          </goal>
+         </transf>
+         </goal>
+        </transf>
+        </goal>
+       </transf>
+       </goal>
+      </transf>
+      </goal>
+     </transf>
+     </goal>
+    </transf>
+    </goal>
+   </transf>
+   </goal>
+  </transf>
+  </goal>
+ </transf>
+ </goal>
+</theory>
 <theory name="M_creusot_contracts__stdqy35z1__iter__fuse__qyi10730559947553418603__produces_refl__refines" proved="true">
  <goal name="refines" proved="true">
  <proof prover="3"><result status="valid" time="0.024500" steps="2"/></proof>
@@ -2477,7 +2715,7 @@
      <goal name="vc_produces_trans&#39;0.0.1.0.1" proved="true">
      <transf name="exists" proved="true" arg1="(s++s1)">
       <goal name="vc_produces_trans&#39;0.0.1.0.1.0" proved="true">
-      <proof prover="3"><result status="valid" time="0.355761" steps="2012"/></proof>
+      <proof prover="3"><result status="valid" time="0.149308" steps="2012"/></proof>
       </goal>
      </transf>
      </goal>
@@ -2552,7 +2790,7 @@
         <proof prover="3"><result status="valid" time="0.021964" steps="204"/></proof>
         </goal>
         <goal name="vc_produces_trans&#39;0.0.1.0.1.0.0.7" proved="true">
-        <proof prover="3"><result status="valid" time="0.185671" steps="722"/></proof>
+        <proof prover="3"><result status="valid" time="0.055485" steps="722"/></proof>
         </goal>
         <goal name="vc_produces_trans&#39;0.0.1.0.1.0.0.8" proved="true">
         <transf name="instantiate" proved="true" arg1="H2" arg2="i">
@@ -2570,7 +2808,7 @@
          <goal name="vc_produces_trans&#39;0.0.1.0.1.0.0.9.0" proved="true">
          <transf name="instantiate" proved="true" arg1="H10" arg2="(i-length ab)">
           <goal name="vc_produces_trans&#39;0.0.1.0.1.0.0.9.0.0" proved="true">
-          <proof prover="3"><result status="valid" time="0.492531" steps="3575"/></proof>
+          <proof prover="3"><result status="valid" time="0.325584" steps="3575"/></proof>
           </goal>
          </transf>
          </goal>
@@ -2760,6 +2998,26 @@
  <proof prover="3"><result status="valid" time="0.051041" steps="148"/></proof>
  </goal>
 </theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__range__qyi16137414346896623968__produces_back_refl__refines" proved="true">
+ <goal name="refines" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.025988" steps="0"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__range__qyi16137414346896623968__produces_back_refl" proved="true">
+ <goal name="vc_produces_back_refl&#39;0" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.028563" steps="10"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__range__qyi16137414346896623968__produces_back_trans__refines" proved="true">
+ <goal name="refines" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.026559" steps="0"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__range__qyi16137414346896623968__produces_back_trans" proved="true">
+ <goal name="vc_produces_back_trans&#39;0" proved="true">
+ <proof prover="2"><result status="valid" time="0.032551" steps="3412"/></proof>
+ </goal>
+</theory>
 <theory name="M_creusot_contracts__stdqy35z1__iter__range__range_inclusive_len" proved="true">
  <goal name="vc_range_inclusive_len&#39;0" proved="true">
  <proof prover="3"><result status="valid" time="0.020449" steps="4"/></proof>
@@ -2785,6 +3043,26 @@
  <proof prover="3"><result status="valid" time="0.042208" steps="143"/></proof>
  </goal>
 </theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__range__qyi12106466433038921999__produces_back_refl__refines" proved="true">
+ <goal name="refines" proved="true">
+ <proof prover="1"><result status="valid" time="0.024887" steps="607"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__range__qyi12106466433038921999__produces_back_refl" proved="true">
+ <goal name="vc_produces_back_refl&#39;0" proved="true">
+ <proof prover="2"><result status="valid" time="0.025755" steps="1861"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__range__qyi12106466433038921999__produces_back_trans__refines" proved="true">
+ <goal name="refines" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.016712" steps="0"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__range__qyi12106466433038921999__produces_back_trans" proved="true">
+ <goal name="vc_produces_back_trans&#39;0" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.053123" steps="143"/></proof>
+ </goal>
+</theory>
 <theory name="M_creusot_contracts__stdqy35z1__iter__repeat__qyi8658929399712466629__produces_refl__refines" proved="true">
  <goal name="refines" proved="true">
  <proof prover="3"><result status="valid" time="0.008767" steps="0"/></proof>
@@ -2805,6 +3083,26 @@
  <proof prover="3"><result status="valid" time="0.029496" steps="48"/></proof>
  </goal>
 </theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__rev__qyi4378764544541057436__produces_refl__refines" proved="true">
+ <goal name="refines" proved="true">
+ <proof prover="1"><result status="valid" time="0.015105" steps="2093"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__rev__qyi4378764544541057436__produces_refl" proved="true">
+ <goal name="vc_produces_refl&#39;0" proved="true">
+ <proof prover="0"><result status="valid" time="0.030403" steps="7363"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__rev__qyi4378764544541057436__produces_trans__refines" proved="true">
+ <goal name="refines" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.014117" steps="0"/></proof>
+ </goal>
+</theory>
+<theory name="M_creusot_contracts__stdqy35z1__iter__rev__qyi4378764544541057436__produces_trans" proved="true">
+ <goal name="vc_produces_trans&#39;0" proved="true">
+ <proof prover="3" timelimit="5"><result status="valid" time="0.012847" steps="16"/></proof>
+ </goal>
+</theory>
 <theory name="M_creusot_contracts__stdqy35z1__iter__skip__qyi14372835745621067113__resolve_coherence__refines" proved="true">
  <goal name="refines" proved="true">
  <proof prover="3"><result status="valid" time="0.018458" steps="2"/></proof>
diff --git a/creusot/tests/creusot-contracts/creusot-contracts/why3shapes.gz b/creusot/tests/creusot-contracts/creusot-contracts/why3shapes.gz
index 928b3d061..b93bff03d 100644
Binary files a/creusot/tests/creusot-contracts/creusot-contracts/why3shapes.gz and b/creusot/tests/creusot-contracts/creusot-contracts/why3shapes.gz differ
diff --git a/creusot/tests/should_succeed/100doors.coma b/creusot/tests/should_succeed/100doors.coma
index ef30ab805..89811ac50 100644
--- a/creusot/tests/should_succeed/100doors.coma
+++ b/creusot/tests/should_succeed/100doors.coma
@@ -15,10 +15,10 @@ module M_100doors__f [#"100doors.rs" 18 0 18 10]
   let%span s100doors13 = "100doors.rs" 26 29 26 30
   let%span svec14 = "../../../creusot-contracts/src/std/vec.rs" 180 22 180 41
   let%span svec15 = "../../../creusot-contracts/src/std/vec.rs" 181 22 181 76
-  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span svec17 = "../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   let%span srange18 = "../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter19 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter19 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span svec20 = "../../../creusot-contracts/src/std/vec.rs" 162 27 162 46
   let%span svec21 = "../../../creusot-contracts/src/std/vec.rs" 163 26 163 54
   let%span svec22 = "../../../creusot-contracts/src/std/vec.rs" 152 27 152 46
@@ -27,8 +27,8 @@ module M_100doors__f [#"100doors.rs" 18 0 18 10]
   let%span svec25 = "../../../creusot-contracts/src/std/vec.rs" 155 26 155 62
   let%span svec26 = "../../../creusot-contracts/src/std/vec.rs" 156 26 156 55
   let%span sindex27 = "../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
-  let%span siter28 = "../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter29 = "../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter28 = "../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter29 = "../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange30 = "../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange31 = "../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange32 = "../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
diff --git a/creusot/tests/should_succeed/bug/164.coma b/creusot/tests/should_succeed/bug/164.coma
index 2780aeba4..b76abe139 100644
--- a/creusot/tests/should_succeed/bug/164.coma
+++ b/creusot/tests/should_succeed/bug/164.coma
@@ -27,11 +27,11 @@ module M_164__main [#"164.rs" 5 0 5 13]
   let%span s16425 = "164.rs" 61 4 61 7
   let%span s16426 = "164.rs" 60 16 60 27
   let%span s16427 = "164.rs" 61 4 61 7
-  let%span siter28 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter28 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span srange29 = "../../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter30 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
-  let%span siter31 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter32 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter30 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
+  let%span siter31 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter32 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange33 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange34 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange35 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
diff --git a/creusot/tests/should_succeed/cc/array.coma b/creusot/tests/should_succeed/cc/array.coma
index 75f935b70..3199e1060 100644
--- a/creusot/tests/should_succeed/cc/array.coma
+++ b/creusot/tests/should_succeed/cc/array.coma
@@ -3,11 +3,11 @@ module M_array__test_array [#"array.rs" 3 0 3 19]
   let%span sarray1 = "array.rs" 4 17 4 18
   let%span sarray2 = "array.rs" 4 20 4 21
   let%span sslice3 = "../../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
-  let%span siter4 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter4 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span sarray5 = "array.rs" 5 31 5 32
   let%span soption6 = "../../../../creusot-contracts/src/std/option.rs" 23 26 23 75
   let%span sarray7 = "array.rs" 6 31 6 32
-  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span sarray9 = "array.rs" 10 30 10 31
   let%span sslice10 = "../../../../creusot-contracts/src/std/slice.rs" 398 20 398 61
   let%span sslice11 = "../../../../creusot-contracts/src/std/slice.rs" 405 12 405 66
diff --git a/creusot/tests/should_succeed/cc/collections.coma b/creusot/tests/should_succeed/cc/collections.coma
index f8345c7cc..420651540 100644
--- a/creusot/tests/should_succeed/cc/collections.coma
+++ b/creusot/tests/should_succeed/cc/collections.coma
@@ -3,8 +3,8 @@ module M_collections__roundtrip_hashmap_into_iter [#"collections.rs" 15 0 17 18]
   let%span scollections1 = "collections.rs" 22 8 25 80
   let%span scollections2 = "collections.rs" 27 20 27 79
   let%span scollections3 = "collections.rs" 14 10 14 24
-  let%span siter4 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
-  let%span siter5 = "../../../../creusot-contracts/src/std/iter.rs" 166 26 167 120
+  let%span siter4 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
+  let%span siter5 = "../../../../creusot-contracts/src/std/iter.rs" 208 26 209 120
   let%span shash_map6 = "../../../../creusot-contracts/src/std/collections/hash_map.rs" 73 20 73 54
   let%span shash_map7 = "../../../../creusot-contracts/src/std/collections/hash_map.rs" 56 12 66 29
   let%span sfmap8 = "../../../../creusot-contracts/src/logic/fmap.rs" 92 8 95 9
@@ -371,7 +371,7 @@ module M_collections__roundtrip_hashmap_iter [#"collections.rs" 32 0 32 97]
   let%span scollections1 = "collections.rs" 38 4 41 77
   let%span scollections2 = "collections.rs" 31 10 31 98
   let%span shash_map3 = "../../../../creusot-contracts/src/std/collections/hash_map.rs" 23 0 37 1
-  let%span siter4 = "../../../../creusot-contracts/src/std/iter.rs" 166 26 167 120
+  let%span siter4 = "../../../../creusot-contracts/src/std/iter.rs" 208 26 209 120
   let%span shash_map5 = "../../../../creusot-contracts/src/std/collections/hash_map.rs" 125 20 125 54
   let%span shash_map6 = "../../../../creusot-contracts/src/std/collections/hash_map.rs" 108 12 118 29
   let%span sfmap7 = "../../../../creusot-contracts/src/logic/fmap.rs" 92 8 95 9
@@ -691,7 +691,7 @@ module M_collections__roundtrip_hashmap_iter_mut [#"collections.rs" 48 0 50 24]
   let%span scollections3 = "collections.rs" 46 10 46 107
   let%span scollections4 = "collections.rs" 47 10 47 110
   let%span shash_map5 = "../../../../creusot-contracts/src/std/collections/hash_map.rs" 23 0 37 1
-  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 166 26 167 120
+  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 208 26 209 120
   let%span shash_map7 = "../../../../creusot-contracts/src/std/collections/hash_map.rs" 177 20 177 54
   let%span shash_map8 = "../../../../creusot-contracts/src/std/collections/hash_map.rs" 160 12 170 29
   let%span sfmap9 = "../../../../creusot-contracts/src/logic/fmap.rs" 92 8 95 9
@@ -1068,27 +1068,27 @@ module M_collections__roundtrip_hashmap_iter_mut [#"collections.rs" 48 0 50 24]
 end
 module M_collections__roundtrip_hashset_into_iter [#"collections.rs" 64 0 64 90]
   let%span scollections0 = "collections.rs" 63 10 63 24
-  let%span siter1 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
-  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 166 26 167 120
-  let%span shash_set3 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 157 20 157 24
-  let%span shash_set4 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 163 20 163 33
-  let%span shash_set5 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 96 20 96 38
-  let%span shash_set6 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 90 8 90 38
-  let%span shash_set7 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 185 20 185 121
-  let%span shash_set8 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 101 14 101 45
-  let%span shash_set9 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 99 4 99 10
-  let%span shash_set10 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 106 15 106 32
-  let%span shash_set11 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 107 15 107 32
-  let%span shash_set12 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 108 14 108 42
-  let%span shash_set13 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 110 8 110 43
+  let%span siter1 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
+  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 208 26 209 120
+  let%span shash_set3 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 163 20 163 24
+  let%span shash_set4 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 169 20 169 33
+  let%span shash_set5 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 102 20 102 38
+  let%span shash_set6 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 96 8 96 38
+  let%span shash_set7 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 191 20 191 121
+  let%span shash_set8 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 107 14 107 45
+  let%span shash_set9 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 105 4 105 10
+  let%span shash_set10 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 112 15 112 32
+  let%span shash_set11 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 113 15 113 32
+  let%span shash_set12 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 114 14 114 42
+  let%span shash_set13 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 116 8 116 43
   let%span smodel14 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
-  let%span shash_set15 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+  let%span shash_set15 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset16 = "../../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span sseq17 = "../../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
-  let%span shash_set18 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 71 11 71 33
-  let%span shash_set19 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 72 11 72 33
-  let%span shash_set20 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 73 10 73 43
-  let%span shash_set21 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 81 4 81 31
+  let%span shash_set18 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 77 11 77 33
+  let%span shash_set19 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 78 11 78 33
+  let%span shash_set20 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 79 10 79 43
+  let%span shash_set21 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 87 4 87 31
   let%span sseq22 = "../../../../creusot-contracts/src/logic/seq.rs" 382 14 383 65
   let%span sseq23 = "../../../../creusot-contracts/src/logic/seq.rs" 381 4 381 12
   
@@ -1372,27 +1372,27 @@ module M_collections__roundtrip_hashset_into_iter [#"collections.rs" 64 0 64 90]
 end
 module M_collections__roundtrip_hashset_iter [#"collections.rs" 69 0 69 87]
   let%span scollections0 = "collections.rs" 68 10 68 24
-  let%span shash_set1 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 19 0 38 1
-  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 166 26 167 120
+  let%span shash_set1 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 19 0 44 1
+  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 208 26 209 120
   let%span smodel3 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
-  let%span shash_set4 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 135 20 135 38
-  let%span shash_set5 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 129 8 129 38
-  let%span shash_set6 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 185 20 185 121
-  let%span shash_set7 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 140 14 140 45
-  let%span shash_set8 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 138 4 138 10
-  let%span shash_set9 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 145 15 145 32
-  let%span shash_set10 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 146 15 146 32
-  let%span shash_set11 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 147 14 147 42
-  let%span shash_set12 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 149 8 149 43
+  let%span shash_set4 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 141 20 141 38
+  let%span shash_set5 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 135 8 135 38
+  let%span shash_set6 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 191 20 191 121
+  let%span shash_set7 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 146 14 146 45
+  let%span shash_set8 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 144 4 144 10
+  let%span shash_set9 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 151 15 151 32
+  let%span shash_set10 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 152 15 152 32
+  let%span shash_set11 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 153 14 153 42
+  let%span shash_set12 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 155 8 155 43
   let%span smodel13 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
-  let%span shash_set14 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
+  let%span shash_set14 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
   let%span sfset15 = "../../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span smodel16 = "../../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span sseq17 = "../../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
-  let%span shash_set18 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 71 11 71 33
-  let%span shash_set19 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 72 11 72 33
-  let%span shash_set20 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 73 10 73 43
-  let%span shash_set21 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 81 4 81 31
+  let%span shash_set18 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 77 11 77 33
+  let%span shash_set19 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 78 11 78 33
+  let%span shash_set20 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 79 10 79 43
+  let%span shash_set21 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 87 4 87 31
   let%span sseq22 = "../../../../creusot-contracts/src/logic/seq.rs" 382 14 383 65
   let%span sseq23 = "../../../../creusot-contracts/src/logic/seq.rs" 381 4 381 12
   
@@ -1615,35 +1615,35 @@ end
 module M_collections__hashset_intersection [#"collections.rs" 74 0 77 15]
   let%span scollections0 = "collections.rs" 73 10 73 42
   let%span shash_set1 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 32 30 32 67
-  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
-  let%span siter3 = "../../../../creusot-contracts/src/std/iter.rs" 166 26 167 120
+  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
+  let%span siter3 = "../../../../creusot-contracts/src/std/iter.rs" 208 26 209 120
   let%span smodel4 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
   let%span scopied5 = "../../../../creusot-contracts/src/std/iter/copied.rs" 11 14 11 39
   let%span scopied6 = "../../../../creusot-contracts/src/std/iter/copied.rs" 40 12 40 105
   let%span scopied7 = "../../../../creusot-contracts/src/std/iter/copied.rs" 48 12 51 79
-  let%span shash_set8 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 185 20 185 121
+  let%span shash_set8 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 191 20 191 121
   let%span scopied9 = "../../../../creusot-contracts/src/std/iter/copied.rs" 21 8 21 29
   let%span scopied10 = "../../../../creusot-contracts/src/std/iter/copied.rs" 57 14 57 45
   let%span scopied11 = "../../../../creusot-contracts/src/std/iter/copied.rs" 62 15 62 32
   let%span scopied12 = "../../../../creusot-contracts/src/std/iter/copied.rs" 63 15 63 32
   let%span scopied13 = "../../../../creusot-contracts/src/std/iter/copied.rs" 64 14 64 42
-  let%span shash_set14 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 210 20 210 56
-  let%span shash_set15 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 204 8 204 38
+  let%span shash_set14 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 216 20 216 56
+  let%span shash_set15 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 210 8 210 38
   let%span sfset16 = "../../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
   let%span sseq17 = "../../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
-  let%span shash_set18 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 215 14 215 45
-  let%span shash_set19 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 213 4 213 10
-  let%span shash_set20 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 220 15 220 32
-  let%span shash_set21 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 221 15 221 32
-  let%span shash_set22 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 222 14 222 42
-  let%span shash_set23 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 224 8 224 43
+  let%span shash_set18 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 221 14 221 45
+  let%span shash_set19 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 219 4 219 10
+  let%span shash_set20 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 226 15 226 32
+  let%span shash_set21 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 227 15 227 32
+  let%span shash_set22 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 228 14 228 42
+  let%span shash_set23 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 230 8 230 43
   let%span sresolve24 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
   let%span smodel25 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
-  let%span shash_set26 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 58 16 65 23
-  let%span shash_set27 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 71 11 71 33
-  let%span shash_set28 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 72 11 72 33
-  let%span shash_set29 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 73 10 73 43
-  let%span shash_set30 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 81 4 81 31
+  let%span shash_set26 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 64 16 71 23
+  let%span shash_set27 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 77 11 77 33
+  let%span shash_set28 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 78 11 78 33
+  let%span shash_set29 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 79 10 79 43
+  let%span shash_set30 = "../../../../creusot-contracts/src/std/collections/hash_set.rs" 87 4 87 31
   let%span smodel31 = "../../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span sseq32 = "../../../../creusot-contracts/src/logic/seq.rs" 382 14 383 65
   let%span sseq33 = "../../../../creusot-contracts/src/logic/seq.rs" 381 4 381 12
diff --git a/creusot/tests/should_succeed/cc/fset.coma b/creusot/tests/should_succeed/cc/fset.coma
new file mode 100644
index 000000000..3f37cef7b
--- /dev/null
+++ b/creusot/tests/should_succeed/cc/fset.coma
@@ -0,0 +1,96 @@
+module M_fset__map_spec [#"fset.rs" 8 0 8 23]
+  let%span sfset0 = "fset.rs" 7 10 7 123
+  let%span sfset1 = "../../../../creusot-contracts/src/logic/fset.rs" 231 8 231 27
+  let%span sfset2 = "../../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  
+  use prelude.prelude.Intrinsic
+  
+  type t_T'0
+  
+  use set.Fset
+  
+  type t_U'0
+  
+  use map.Map
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  function map'0 (self : Fset.fset t_T'0) (f : Map.map t_T'0 t_U'0) : Fset.fset t_U'0 =
+    [%#sfset1] Fset.map f self
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] (self : Fset.fset t_U'0) (e : t_U'0) =
+    [%#sfset2] Fset.mem e self
+  
+  use set.Fset
+  
+  predicate contains'1 [@inline:trivial] (self : Fset.fset t_T'0) (e : t_T'0) =
+    [%#sfset2] Fset.mem e self
+  
+  use map.Map
+  
+  meta "compute_max_steps" 1000000
+  
+  let rec map_spec'0 (_1:()) (return'  (ret:()))= (! bb0 [ bb0 = return' {_0} ] ) [ & _0 : () = any_l () ] 
+    [ return' (result:())-> {[@expl:map_spec ensures] [%#sfset0] forall xs : Fset.fset t_T'0, f : Map.map t_T'0 t_U'0, y : t_U'0 . contains'0 (map'0 xs f) y
+      = (exists x : t_T'0 . contains'1 xs x /\ Map.get f x = y)}
+      (! return' {result}) ]
+    
+end
+module M_fset__filter_spec [#"fset.rs" 11 0 11 23]
+  let%span sfset0 = "fset.rs" 10 10 10 113
+  let%span sfset1 = "../../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  
+  use prelude.prelude.Intrinsic
+  
+  type t_T'0
+  
+  use set.Fset
+  
+  use map.Map
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] (self : Fset.fset t_T'0) (e : t_T'0) =
+    [%#sfset1] Fset.mem e self
+  
+  use map.Map
+  
+  meta "compute_max_steps" 1000000
+  
+  let rec filter_spec'0 (_1:()) (return'  (ret:()))= (! bb0 [ bb0 = return' {_0} ] ) [ & _0 : () = any_l () ] 
+    [ return' (result:())-> {[@expl:filter_spec ensures] [%#sfset0] forall xs : Fset.fset t_T'0, f : Map.map t_T'0 bool, x : t_T'0 . contains'0 (Fset.filter xs f) x
+      = (contains'0 xs x /\ Map.get f x)}
+      (! return' {result}) ]
+    
+end
+module M_fset__interval_spec [#"fset.rs" 14 0 14 22]
+  let%span sfset0 = "fset.rs" 13 10 13 94
+  let%span sfset1 = "../../../../creusot-contracts/src/logic/fset.rs" 46 8 46 26
+  
+  use prelude.prelude.Intrinsic
+  
+  use prelude.prelude.Int
+  
+  use set.FsetInt
+  
+  use set.Fset
+  
+  use set.Fset
+  
+  predicate contains'0 [@inline:trivial] (self : Fset.fset int) (e : int) =
+    [%#sfset1] Fset.mem e self
+  
+  meta "compute_max_steps" 1000000
+  
+  let rec interval_spec'0 (_1:()) (return'  (ret:()))= (! bb0 [ bb0 = return' {_0} ] ) [ & _0 : () = any_l () ] 
+    [ return' (result:())-> {[@expl:interval_spec ensures] [%#sfset0] forall i : int, j : int, k : int . contains'0 (FsetInt.interval i j) k
+      = (i <= k /\ k < j)}
+      (! return' {result}) ]
+    
+end
diff --git a/creusot/tests/should_succeed/cc/fset.rs b/creusot/tests/should_succeed/cc/fset.rs
new file mode 100644
index 000000000..1c2bbab18
--- /dev/null
+++ b/creusot/tests/should_succeed/cc/fset.rs
@@ -0,0 +1,14 @@
+extern crate creusot_contracts;
+use creusot_contracts::{
+    logic::{FSet, Mapping},
+    *,
+};
+
+#[ensures(forall<xs: FSet<T>, f: Mapping<T, U>, y: U> xs.map(f).contains(y) == exists<x: T> xs.contains(x) && f.get(x) == y)]
+pub fn map_spec<T, U>() {}
+
+#[ensures(forall<xs: FSet<T>, f: Mapping<T, bool>, x: T> xs.filter(f).contains(x) == (xs.contains(x) && f.get(x)))]
+pub fn filter_spec<T>() {}
+
+#[ensures(forall<i: Int, j: Int, k: Int> FSet::interval(i, j).contains(k) == (i <= k && k < j))]
+pub fn interval_spec() {}
diff --git a/creusot/tests/should_succeed/cc/fset/why3session.xml b/creusot/tests/should_succeed/cc/fset/why3session.xml
new file mode 100644
index 000000000..26600bd03
--- /dev/null
+++ b/creusot/tests/should_succeed/cc/fset/why3session.xml
@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE why3session PUBLIC "-//Why3//proof session v5//EN"
+"https://www.why3.org/why3session.dtd">
+<why3session shape_version="6">
+<prover id="0" name="Alt-Ergo" version="2.6.0" timelimit="5" steplimit="0" memlimit="1000"/>
+<file format="coma" proved="true">
+<path name=".."/><path name="fset.coma"/>
+<theory name="M_fset__map_spec" proved="true">
+ <goal name="vc_map_spec&#39;0" proved="true">
+ <proof prover="0"><result status="valid" time="0.018326" steps="24"/></proof>
+ </goal>
+</theory>
+<theory name="M_fset__filter_spec" proved="true">
+ <goal name="vc_filter_spec&#39;0" proved="true">
+ <proof prover="0"><result status="valid" time="0.019114" steps="4"/></proof>
+ </goal>
+</theory>
+<theory name="M_fset__interval_spec" proved="true">
+ <goal name="vc_interval_spec&#39;0" proved="true">
+ <proof prover="0"><result status="valid" time="0.017611" steps="6"/></proof>
+ </goal>
+</theory>
+</file>
+</why3session>
diff --git a/creusot/tests/should_succeed/cc/fset/why3shapes.gz b/creusot/tests/should_succeed/cc/fset/why3shapes.gz
new file mode 100644
index 000000000..bf1e1f1e0
Binary files /dev/null and b/creusot/tests/should_succeed/cc/fset/why3shapes.gz differ
diff --git a/creusot/tests/should_succeed/cc/iter.coma b/creusot/tests/should_succeed/cc/iter.coma
index ddb4b17c1..ba4fc7129 100644
--- a/creusot/tests/should_succeed/cc/iter.coma
+++ b/creusot/tests/should_succeed/cc/iter.coma
@@ -1,11 +1,11 @@
-module M_iter__test_mut_ref [#"iter.rs" 3 0 3 21]
-  let%span siter0 = "iter.rs" 4 17 4 18
-  let%span siter1 = "iter.rs" 4 20 4 21
+module M_iter__test_mut_ref [#"iter.rs" 4 0 4 21]
+  let%span siter0 = "iter.rs" 5 17 5 18
+  let%span siter1 = "iter.rs" 5 20 5 21
   let%span sslice2 = "../../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
-  let%span siter3 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
-  let%span siter4 = "iter.rs" 5 38 5 39
+  let%span siter3 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
+  let%span siter4 = "iter.rs" 6 38 6 39
   let%span soption5 = "../../../../creusot-contracts/src/std/option.rs" 23 26 23 75
-  let%span siter6 = "iter.rs" 6 38 6 39
+  let%span siter6 = "iter.rs" 7 38 7 39
   let%span sslice7 = "../../../../creusot-contracts/src/std/slice.rs" 398 20 398 61
   let%span sslice8 = "../../../../creusot-contracts/src/std/slice.rs" 405 12 405 66
   let%span sresolve9 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
@@ -333,3 +333,1086 @@ module M_iter__test_mut_ref [#"iter.rs" 3 0 3 21]
     | & _78 : array int32 = any_l () ]
      [ return' (result:())-> (! return' {result}) ] 
 end
+module M_iter__test_filter [#"iter.rs" 11 0 11 20]
+  let%span siter0 = "iter.rs" 12 17 12 21
+  let%span siter1 = "iter.rs" 12 23 12 28
+  let%span siter2 = "iter.rs" 12 30 12 34
+  let%span sslice3 = "../../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
+  let%span siter4 = "iter.rs" 13 18 13 31
+  let%span siter5 = "../../../../creusot-contracts/src/std/iter.rs" 175 27 175 47
+  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 176 27 176 53
+  let%span siter7 = "../../../../creusot-contracts/src/std/iter.rs" 177 27 177 45
+  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
+  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
+  let%span siter10 = "iter.rs" 16 38 16 42
+  let%span soption11 = "../../../../creusot-contracts/src/std/option.rs" 23 26 23 75
+  let%span siter12 = "iter.rs" 17 38 17 42
+  let%span sfilter13 = "../../../../creusot-contracts/src/std/iter/filter.rs" 58 16 58 59
+  let%span sfilter14 = "../../../../creusot-contracts/src/std/iter/filter.rs" 50 16 50 57
+  let%span sfilter15 = "../../../../creusot-contracts/src/std/iter/filter.rs" 65 16 65 126
+  let%span sfilter16 = "../../../../creusot-contracts/src/std/iter/filter.rs" 15 14 15 39
+  let%span sfilter17 = "../../../../creusot-contracts/src/std/iter/filter.rs" 22 14 22 39
+  let%span sfilter18 = "../../../../creusot-contracts/src/std/iter/filter.rs" 77 12 79 47
+  let%span sfilter19 = "../../../../creusot-contracts/src/std/iter/filter.rs" 87 12 98 143
+  let%span sresolve20 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
+  let%span smodel21 = "../../../../creusot-contracts/src/model.rs" 83 8 83 28
+  let%span sops22 = "../../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
+  let%span sops23 = "../../../../creusot-contracts/src/std/ops.rs" 110 14 110 36
+  let%span sops24 = "../../../../creusot-contracts/src/std/ops.rs" 115 14 115 31
+  let%span sops25 = "../../../../creusot-contracts/src/std/ops.rs" 120 15 120 29
+  let%span sops26 = "../../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
+  let%span sops27 = "../../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
+  let%span sops28 = "../../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
+  let%span sfilter29 = "../../../../creusot-contracts/src/std/iter/filter.rs" 104 14 104 45
+  let%span sfilter30 = "../../../../creusot-contracts/src/std/iter/filter.rs" 109 15 109 32
+  let%span sfilter31 = "../../../../creusot-contracts/src/std/iter/filter.rs" 110 15 110 32
+  let%span sfilter32 = "../../../../creusot-contracts/src/std/iter/filter.rs" 111 14 111 42
+  let%span sslice33 = "../../../../creusot-contracts/src/std/slice.rs" 405 12 405 66
+  let%span sslice34 = "../../../../creusot-contracts/src/std/slice.rs" 398 20 398 61
+  let%span sinvariant35 = "../../../../creusot-contracts/src/invariant.rs" 34 20 34 44
+  let%span soption36 = "../../../../creusot-contracts/src/std/option.rs" 11 8 14 9
+  let%span sslice37 = "../../../../creusot-contracts/src/std/slice.rs" 411 14 411 45
+  let%span sslice38 = "../../../../creusot-contracts/src/std/slice.rs" 409 4 409 10
+  let%span sslice39 = "../../../../creusot-contracts/src/std/slice.rs" 416 15 416 32
+  let%span sslice40 = "../../../../creusot-contracts/src/std/slice.rs" 417 15 417 32
+  let%span sslice41 = "../../../../creusot-contracts/src/std/slice.rs" 418 14 418 42
+  let%span sslice42 = "../../../../creusot-contracts/src/std/slice.rs" 414 4 414 10
+  let%span sslice43 = "../../../../creusot-contracts/src/std/slice.rs" 96 14 96 41
+  let%span sslice44 = "../../../../creusot-contracts/src/std/slice.rs" 97 14 97 80
+  let%span smodel45 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
+  let%span sslice46 = "../../../../creusot-contracts/src/std/slice.rs" 28 14 28 41
+  let%span sslice47 = "../../../../creusot-contracts/src/std/slice.rs" 29 14 29 42
+  let%span smodel48 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
+  let%span sindex49 = "../../../../creusot-contracts/src/logic/ops/index.rs" 49 8 49 31
+  let%span smodel50 = "../../../../creusot-contracts/src/model.rs" 120 8 120 12
+  
+  use prelude.prelude.Slice
+  
+  use prelude.prelude.Borrow
+  
+  use prelude.prelude.Intrinsic
+  
+  let rec promoted3__test_filter'0 (return'  (ret:array bool))= bb0
+    [ bb0 = s0
+      [ s0 = any
+        [ any_ (__arr_temp:array bool)-> (! -{Seq.get __arr_temp.elts 0
+          /\ Seq.get __arr_temp.elts 1 = ([%#siter1] false)
+          /\ Seq.get __arr_temp.elts 2 /\ Seq.length __arr_temp.elts = 3}-
+           [ &_1 <- __arr_temp ] 
+          s1) ]
+        
+      | s1 =  [ &_0 <- _1 ] s2
+      | s2 = return' {_0} ]
+       ]
+     [ & _0 : array bool = any_l () | & _1 : array bool = any_l () ] 
+    [ return' (result:array bool)-> return' {result} ]
+    
+  
+  predicate inv'2 (_1 : slice bool)
+  
+  axiom inv_axiom'2 [@rewrite] : forall x : slice bool [inv'2 x] . inv'2 x = true
+  
+  use prelude.prelude.Opaque
+  
+  type t_NonNull'0  =
+    { t_NonNull__pointer'0: opaque_ptr }
+  
+  type t_Iter'0  =
+    { t_Iter__ptr'0: t_NonNull'0; t_Iter__end_or_len'0: opaque_ptr; t_Iter__qy95zmarker'0: () }
+  
+  function view'0 (self : t_Iter'0) : slice bool
+  
+  let rec iter'0 (self:slice bool) (return'  (ret:t_Iter'0))= {[@expl:iter 'self' type invariant] inv'2 self}
+    any [ return' (result:t_Iter'0)-> {[%#sslice3] view'0 result = self} (! return' {result}) ] 
+  
+  predicate resolve'3 (self : borrowed ()) =
+    [%#sresolve20] self.final = self.current
+  
+  predicate resolve'1 (_1 : borrowed ()) =
+    resolve'3 _1
+  
+  predicate postcondition_once'0 (self : ()) (args : bool) (result : bool) =
+    [%#siter4] let (b) = args in result = b
+  
+  predicate resolve'4 (_1 : ()) =
+    true
+  
+  predicate unnest'0 (self : ()) (_2 : ()) =
+    true
+  
+  predicate postcondition_mut'1 (self : ()) (args : bool) (result_state : ()) (result : bool) =
+    (let (b) = args in result = b) /\ unnest'0 self result_state
+  
+  function fn_mut_once'0 (self : ()) (args : bool) (res : bool) : ()
+  
+  axiom fn_mut_once'0_spec : forall self : (), args : bool, res : bool . [%#sops28] postcondition_once'0 self args res
+  = (exists res_state : () . postcondition_mut'1 self args res_state res /\ resolve'4 res_state)
+  
+  function unnest_trans'0 (self : ()) (b : ()) (c : ()) : ()
+  
+  axiom unnest_trans'0_spec : forall self : (), b : (), c : () . ([%#sops25] unnest'0 self b)
+   -> ([%#sops26] unnest'0 b c)  -> ([%#sops27] unnest'0 self c)
+  
+  function unnest_refl'0 (self : ()) : ()
+  
+  axiom unnest_refl'0_spec : forall self : () . [%#sops24] unnest'0 self self
+  
+  function postcondition_mut_unnest'0 (self : ()) (args : bool) (res_state : ()) (res : bool) : ()
+  
+  axiom postcondition_mut_unnest'0_spec : forall self : (), args : bool, res_state : (), res : bool . ([%#sops22] postcondition_mut'1 self args res_state res)
+   -> ([%#sops23] unnest'0 self res_state)
+  
+  let rec closure0'0 (_1:borrowed ()) (b:bool) (return'  (ret:bool))= (! bb0
+    [ bb0 = s0 [ s0 = -{resolve'1 _1}- s1 | s1 =  [ &res <- b ] s2 | s2 =  [ &_0 <- res ] s3 | s3 = return' {_0} ]  ]
+    ) [ & _0 : bool = any_l () | & _1 : borrowed () = _1 | & b : bool = b | & res : bool = any_l () ] 
+    [ return' (result:bool)-> {[@expl:closure ensures] [%#siter4] result = b}
+      {[@expl:closure unnest] unnest'0 _1.current _1.final}
+      (! return' {result}) ]
+    
+  
+  predicate inv'3 (_1 : t_Iter'0)
+  
+  axiom inv_axiom'3 [@rewrite] : forall x : t_Iter'0 [inv'3 x] . inv'3 x = true
+  
+  predicate inv'4 (_1 : ())
+  
+  axiom inv_axiom'4 [@rewrite] : forall x : () [inv'4 x] . inv'4 x = true
+  
+  predicate postcondition_once'1 (self : ()) (args : bool) (result : bool) =
+    [%#siter4] let (b) = args in result = b
+  
+  predicate postcondition_mut'0 (self : ()) (args : bool) (result_state : ()) (result : bool) =
+    (let (b) = args in result = b) /\ unnest'0 self result_state
+  
+  function fn_mut_once'1 (self : ()) (args : bool) (res : bool) : ()
+  
+  axiom fn_mut_once'1_spec : forall self : (), args : bool, res : bool . [%#sops28] postcondition_once'1 self args res
+  = (exists res_state : () . postcondition_mut'0 self args res_state res /\ resolve'4 res_state)
+  
+  predicate unnest'1 (self : ()) (_2 : ()) =
+    true
+  
+  function unnest_trans'1 (self : ()) (b : ()) (c : ()) : ()
+  
+  axiom unnest_trans'1_spec : forall self : (), b : (), c : () . ([%#sops25] unnest'1 self b)
+   -> ([%#sops26] unnest'1 b c)  -> ([%#sops27] unnest'1 self c)
+  
+  function unnest_refl'1 (self : ()) : ()
+  
+  axiom unnest_refl'1_spec : forall self : () . [%#sops24] unnest'1 self self
+  
+  function postcondition_mut_unnest'1 (self : ()) (args : bool) (res_state : ()) (res : bool) : ()
+  
+  axiom postcondition_mut_unnest'1_spec : forall self : (), args : bool, res_state : (), res : bool . ([%#sops22] postcondition_mut'0 self args res_state res)
+   -> ([%#sops23] unnest'1 self res_state)
+  
+  predicate immutable'0 (_1 : ()) =
+    [%#sfilter13] forall f : (), g : () . unnest'1 f g  -> f = g
+  
+  predicate precondition'0 (self : ()) (args : bool) =
+    let (b) = args in true
+  
+  predicate no_precondition'0 (_1 : ()) =
+    [%#sfilter14] forall f : (), i : bool . precondition'0 f (i)
+  
+  predicate precise'0 (_1 : ()) =
+    [%#sfilter15] forall f1 : (), f2 : (), i : bool . not (postcondition_mut'0 f1 (i) f2 true
+    /\ postcondition_mut'0 f1 (i) f2 false)
+  
+  type t_Filter'0  =
+    { t_Filter__iter'0: t_Iter'0; t_Filter__predicate'0: () }
+  
+  predicate invariant'0 (self : t_Filter'0)
+  
+  predicate inv'0 (_1 : t_Filter'0)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_Filter'0 [inv'0 x] . inv'0 x
+  = (invariant'0 x
+  /\ match x with
+    | {t_Filter__iter'0 = iter ; t_Filter__predicate'0 = predicate'} -> true
+    end)
+  
+  function iter'1 (self : t_Filter'0) : t_Iter'0
+  
+  axiom iter'1_spec : forall self : t_Filter'0 . [%#sfilter16] inv'0 self  -> inv'3 (iter'1 self)
+  
+  function func'0 (self : t_Filter'0) : ()
+  
+  axiom func'0_spec : forall self : t_Filter'0 . [%#sfilter17] inv'0 self  -> inv'4 (func'0 self)
+  
+  let rec filter'0 (self:t_Iter'0) (predicate':()) (return'  (ret:t_Filter'0))= {[@expl:filter 'self' type invariant] inv'3 self}
+    {[@expl:filter 'predicate' type invariant] inv'4 predicate'}
+    {[@expl:filter requires #0] [%#siter5] immutable'0 predicate'}
+    {[@expl:filter requires #1] [%#siter6] no_precondition'0 predicate'}
+    {[@expl:filter requires #2] [%#siter7] precise'0 predicate'}
+    any
+    [ return' (result:t_Filter'0)-> {inv'0 result}
+      {[%#siter8] iter'1 result = self /\ func'0 result = predicate'}
+      (! return' {result}) ]
+    
+  
+  predicate invariant'1 (self : borrowed (t_Filter'0)) =
+    [%#sinvariant35] inv'0 self.current /\ inv'0 self.final
+  
+  predicate inv'1 (_1 : borrowed (t_Filter'0))
+  
+  axiom inv_axiom'1 [@rewrite] : forall x : borrowed (t_Filter'0) [inv'1 x] . inv'1 x = invariant'1 x
+  
+  type t_Option'0  =
+    | C_None'0
+    | C_Some'0 bool
+  
+  predicate inv'5 (_1 : t_Option'0)
+  
+  axiom inv_axiom'5 [@rewrite] : forall x : t_Option'0 [inv'5 x] . inv'5 x = true
+  
+  use seq.Seq
+  
+  use prelude.prelude.Int
+  
+  use map.Map
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use prelude.prelude.UIntSize
+  
+  constant v_MAX'0 : usize = (18446744073709551615 : usize)
+  
+  use prelude.prelude.UIntSize
+  
+  use prelude.prelude.Slice
+  
+  function view'2 (self : slice bool) : Seq.seq bool
+  
+  axiom view'2_spec : forall self : slice bool . ([%#sslice46] Seq.length (view'2 self)
+  <= UIntSize.to_int (v_MAX'0 : usize))
+  && ([%#sslice47] view'2 self = Slice.id self)
+  
+  function view'3 (self : slice bool) : Seq.seq bool =
+    [%#smodel48] view'2 self
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  function index_logic'0 [@inline:trivial] (self : slice bool) (ix : int) : bool =
+    [%#sindex49] Seq.get (view'2 self) ix
+  
+  function to_ref_seq'0 (self : slice bool) : Seq.seq bool
+  
+  axiom to_ref_seq'0_spec : forall self : slice bool . ([%#sslice43] Seq.length (to_ref_seq'0 self)
+  = Seq.length (view'3 self))
+  && ([%#sslice44] forall i : int . 0 <= i /\ i < Seq.length (to_ref_seq'0 self)
+   -> Seq.get (to_ref_seq'0 self) i = index_logic'0 self i)
+  
+  predicate produces'1 (self : t_Iter'0) (visited : Seq.seq bool) (tl : t_Iter'0) =
+    [%#sslice33] to_ref_seq'0 (view'0 self) = Seq.(++) visited (to_ref_seq'0 (view'0 tl))
+  
+  function produces_trans'1 (a : t_Iter'0) (ab : Seq.seq bool) (b : t_Iter'0) (bc : Seq.seq bool) (c : t_Iter'0) : () =
+    [%#sslice42] ()
+  
+  axiom produces_trans'1_spec : forall a : t_Iter'0, ab : Seq.seq bool, b : t_Iter'0, bc : Seq.seq bool, c : t_Iter'0 . ([%#sslice39] produces'1 a ab b)
+   -> ([%#sslice40] produces'1 b bc c)  -> ([%#sslice41] produces'1 a (Seq.(++) ab bc) c)
+  
+  function produces_refl'1 (self : t_Iter'0) : () =
+    [%#sslice38] ()
+  
+  axiom produces_refl'1_spec : forall self : t_Iter'0 . [%#sslice37] produces'1 self (Seq.empty  : Seq.seq bool) self
+  
+  use map.Map
+  
+  predicate produces'0 (self : t_Filter'0) (visited : Seq.seq bool) (succ : t_Filter'0) =
+    [%#sfilter19] invariant'0 self
+     -> unnest'1 (func'0 self) (func'0 succ)
+    /\ (exists s : Seq.seq bool, f : Map.map int int . produces'1 (iter'1 self) s (iter'1 succ)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> Seq.get visited i = Seq.get s (Map.get f i))
+    /\ (forall i : int . 0 <= i /\ i < Seq.length s
+     -> (exists j : int . 0 <= j /\ j < Seq.length visited /\ Map.get f j = i)
+    = postcondition_mut'0 (func'0 self) (Seq.get s i) (func'0 self) true))
+  
+  function produces_trans'0 (a : t_Filter'0) (ab : Seq.seq bool) (b : t_Filter'0) (bc : Seq.seq bool) (c : t_Filter'0) : ()
+    
+  
+  axiom produces_trans'0_spec : forall a : t_Filter'0, ab : Seq.seq bool, b : t_Filter'0, bc : Seq.seq bool, c : t_Filter'0 . ([%#sfilter30] produces'0 a ab b)
+   -> ([%#sfilter31] produces'0 b bc c)  -> ([%#sfilter32] produces'0 a (Seq.(++) ab bc) c)
+  
+  function produces_refl'0 (self : t_Filter'0) : ()
+  
+  axiom produces_refl'0_spec : forall self : t_Filter'0 . [%#sfilter29] produces'0 self (Seq.empty  : Seq.seq bool) self
+  
+  predicate resolve'5 (self : borrowed (t_Iter'0)) =
+    [%#sresolve20] self.final = self.current
+  
+  function view'1 (self : borrowed (t_Iter'0)) : slice bool =
+    [%#smodel45] view'0 self.current
+  
+  use seq.Seq
+  
+  predicate completed'1 (self : borrowed (t_Iter'0)) =
+    [%#sslice34] resolve'5 self /\ view'2 (view'1 self) = (Seq.empty  : Seq.seq bool)
+  
+  predicate completed'0 (self : borrowed (t_Filter'0)) =
+    [%#sfilter18] (exists s : Seq.seq bool, e : borrowed (t_Iter'0) . produces'1 (iter'1 self.current) s e.current
+    /\ completed'1 e
+    /\ (forall i : int . 0 <= i /\ i < Seq.length s
+     -> postcondition_mut'0 (func'0 self.current) (Seq.get s i) (func'0 self.final) false))
+    /\ func'0 self.current = func'0 self.final
+  
+  use seq.Seq
+  
+  let rec next'0 (self:borrowed (t_Filter'0)) (return'  (ret:t_Option'0))= {[@expl:next 'self' type invariant] inv'1 self}
+    any
+    [ return' (result:t_Option'0)-> {inv'5 result}
+      {[%#siter9] match result with
+        | C_None'0 -> completed'0 self
+        | C_Some'0 v -> produces'0 self.current (Seq.singleton v) self.final
+        end}
+      (! return' {result}) ]
+    
+  
+  predicate resolve'2 (self : borrowed (t_Filter'0)) =
+    [%#sresolve20] self.final = self.current
+  
+  predicate resolve'0 (_1 : borrowed (t_Filter'0)) =
+    resolve'2 _1
+  
+  let rec promoted2__test_filter'0 (return'  (ret:t_Option'0))= bb0
+    [ bb0 = s0 [ s0 =  [ &_1 <- C_Some'0 ([%#siter10] true) ] s1 | s1 =  [ &_0 <- _1 ] s2 | s2 = return' {_0} ]  ]
+     [ & _0 : t_Option'0 = any_l () | & _1 : t_Option'0 = any_l () ] 
+    [ return' (result:t_Option'0)-> return' {result} ]
+    
+  
+  predicate inv'6 (_1 : t_Option'0)
+  
+  axiom inv_axiom'6 [@rewrite] : forall x : t_Option'0 [inv'6 x] . inv'6 x = true
+  
+  type t_Option'1  =
+    | C_None'1
+    | C_Some'1 bool
+  
+  function deep_model'3 (self : bool) : bool =
+    [%#smodel50] self
+  
+  function deep_model'2 (self : bool) : bool =
+    [%#smodel21] deep_model'3 self
+  
+  function deep_model'1 (self : t_Option'0) : t_Option'1 =
+    [%#soption36] match self with
+      | C_Some'0 t -> C_Some'1 (deep_model'2 t)
+      | C_None'0 -> C_None'1
+      end
+  
+  function deep_model'0 (self : t_Option'0) : t_Option'1 =
+    [%#smodel21] deep_model'1 self
+  
+  let rec eq'0 (self:t_Option'0) (other:t_Option'0) (return'  (ret:bool))= {[@expl:eq 'self' type invariant] inv'6 self}
+    {[@expl:eq 'other' type invariant] inv'6 other}
+    any
+    [ return' (result:bool)-> {[%#soption11] result = (deep_model'0 self = deep_model'0 other)} (! return' {result}) ]
+    
+  
+  let rec promoted1__test_filter'0 (return'  (ret:t_Option'0))= bb0
+    [ bb0 = s0 [ s0 =  [ &_1 <- C_Some'0 ([%#siter12] true) ] s1 | s1 =  [ &_0 <- _1 ] s2 | s2 = return' {_0} ]  ]
+     [ & _0 : t_Option'0 = any_l () | & _1 : t_Option'0 = any_l () ] 
+    [ return' (result:t_Option'0)-> return' {result} ]
+    
+  
+  let rec promoted0__test_filter'0 (return'  (ret:t_Option'0))= bb0
+    [ bb0 = s0 [ s0 =  [ &_1 <- C_None'0 ] s1 | s1 =  [ &_0 <- _1 ] s2 | s2 = return' {_0} ]  ]
+     [ & _0 : t_Option'0 = any_l () | & _1 : t_Option'0 = any_l () ] 
+    [ return' (result:t_Option'0)-> return' {result} ]
+    
+  
+  type t_AssertKind'0  =
+    | C_Eq'0
+    | C_Ne'0
+    | C_Match'0
+  
+  meta "compute_max_steps" 1000000
+  
+  let rec test_filter'0 (_1:()) (return'  (ret:()))= (! bb0
+    [ bb0 = s0
+      [ s0 = promoted3__test_filter'0 (fun (pr3:array bool) ->  [ &_80 <- pr3 ] s1)
+      | s1 = iter'0 {_80} (fun (_ret':t_Iter'0) ->  [ &_2 <- _ret' ] s2)
+      | s2 = bb1 ]
+      
+    | bb1 = s0
+      [ s0 =  [ &_6 <- () ] s1 | s1 = filter'0 {_2} {_6} (fun (_ret':t_Filter'0) ->  [ &a <- _ret' ] s2) | s2 = bb2 ]
+      
+    | bb2 = s0
+      [ s0 = {inv'0 a}
+        Borrow.borrow_mut <t_Filter'0> {a}
+          (fun (_ret':borrowed (t_Filter'0)) ->  [ &_12 <- _ret' ] -{inv'0 _ret'.final}-  [ &a <- _ret'.final ] s1)
+      | s1 = {inv'0 _12.current}
+        Borrow.borrow_final <t_Filter'0> {_12.current} {Borrow.get_id _12}
+          (fun (_ret':borrowed (t_Filter'0)) ->
+             [ &_11 <- _ret' ] 
+            -{inv'0 _ret'.final}-
+             [ &_12 <- { _12 with current = _ret'.final } ] 
+            s2)
+      | s2 = next'0 {_11} (fun (_ret':t_Option'0) ->  [ &_10 <- _ret' ] s3)
+      | s3 = bb3 ]
+      
+    | bb3 = s0
+      [ s0 = {[@expl:type invariant] inv'1 _12} s1
+      | s1 = -{resolve'0 _12}- s2
+      | s2 = promoted2__test_filter'0 (fun (pr2:t_Option'0) ->  [ &_79 <- pr2 ] s3)
+      | s3 =  [ &_8 <- (_10, _79) ] s4
+      | s4 =  [ &left_val <- let (r'0, _) = _8 in r'0 ] s5
+      | s5 =  [ &right_val <- let (_, r'1) = _8 in r'1 ] s6
+      | s6 = eq'0 {left_val} {right_val} (fun (_ret':bool) ->  [ &_19 <- _ret' ] s7)
+      | s7 = bb4 ]
+      
+    | bb4 = any [ br0 -> {_19 = false} (! bb6) | br1 -> {_19} (! bb5) ] 
+    | bb5 = s0
+      [ s0 = {inv'0 a}
+        Borrow.borrow_mut <t_Filter'0> {a}
+          (fun (_ret':borrowed (t_Filter'0)) ->  [ &_36 <- _ret' ] -{inv'0 _ret'.final}-  [ &a <- _ret'.final ] s1)
+      | s1 = {inv'0 _36.current}
+        Borrow.borrow_final <t_Filter'0> {_36.current} {Borrow.get_id _36}
+          (fun (_ret':borrowed (t_Filter'0)) ->
+             [ &_35 <- _ret' ] 
+            -{inv'0 _ret'.final}-
+             [ &_36 <- { _36 with current = _ret'.final } ] 
+            s2)
+      | s2 = next'0 {_35} (fun (_ret':t_Option'0) ->  [ &_34 <- _ret' ] s3)
+      | s3 = bb7 ]
+      
+    | bb7 = s0
+      [ s0 = {[@expl:type invariant] inv'1 _36} s1
+      | s1 = -{resolve'0 _36}- s2
+      | s2 = promoted1__test_filter'0 (fun (pr1:t_Option'0) ->  [ &_78 <- pr1 ] s3)
+      | s3 =  [ &_32 <- (_34, _78) ] s4
+      | s4 =  [ &left_val1 <- let (r'0, _) = _32 in r'0 ] s5
+      | s5 =  [ &right_val1 <- let (_, r'1) = _32 in r'1 ] s6
+      | s6 = eq'0 {left_val1} {right_val1} (fun (_ret':bool) ->  [ &_43 <- _ret' ] s7)
+      | s7 = bb8 ]
+      
+    | bb8 = any [ br0 -> {_43 = false} (! bb10) | br1 -> {_43} (! bb9) ] 
+    | bb9 = s0
+      [ s0 = {inv'0 a}
+        Borrow.borrow_mut <t_Filter'0> {a}
+          (fun (_ret':borrowed (t_Filter'0)) ->  [ &_60 <- _ret' ] -{inv'0 _ret'.final}-  [ &a <- _ret'.final ] s1)
+      | s1 = {inv'0 _60.current}
+        Borrow.borrow_final <t_Filter'0> {_60.current} {Borrow.get_id _60}
+          (fun (_ret':borrowed (t_Filter'0)) ->
+             [ &_59 <- _ret' ] 
+            -{inv'0 _ret'.final}-
+             [ &_60 <- { _60 with current = _ret'.final } ] 
+            s2)
+      | s2 = next'0 {_59} (fun (_ret':t_Option'0) ->  [ &_58 <- _ret' ] s3)
+      | s3 = bb11 ]
+      
+    | bb11 = s0
+      [ s0 = {[@expl:type invariant] inv'1 _60} s1
+      | s1 = -{resolve'0 _60}- s2
+      | s2 = {[@expl:type invariant] inv'0 a} s3
+      | s3 = promoted0__test_filter'0 (fun (pr0:t_Option'0) ->  [ &_77 <- pr0 ] s4)
+      | s4 =  [ &_56 <- (_58, _77) ] s5
+      | s5 =  [ &left_val2 <- let (r'0, _) = _56 in r'0 ] s6
+      | s6 =  [ &right_val2 <- let (_, r'1) = _56 in r'1 ] s7
+      | s7 = eq'0 {left_val2} {right_val2} (fun (_ret':bool) ->  [ &_65 <- _ret' ] s8)
+      | s8 = bb12 ]
+      
+    | bb12 = any [ br0 -> {_65 = false} (! bb14) | br1 -> {_65} (! bb13) ] 
+    | bb13 = return' {_0}
+    | bb14 = s0
+      [ s0 =  [ &kind2 <- C_Eq'0 ] s1
+      | s1 =  [ &_73 <- left_val2 ] s2
+      | s2 =  [ &_75 <- right_val2 ] s3
+      | s3 = {false} any ]
+      
+    | bb10 = s0
+      [ s0 = {[@expl:type invariant] inv'0 a} s1
+      | s1 =  [ &kind1 <- C_Eq'0 ] s2
+      | s2 =  [ &_51 <- left_val1 ] s3
+      | s3 =  [ &_53 <- right_val1 ] s4
+      | s4 = {false} any ]
+      
+    | bb6 = s0
+      [ s0 = {[@expl:type invariant] inv'0 a} s1
+      | s1 =  [ &kind <- C_Eq'0 ] s2
+      | s2 =  [ &_27 <- left_val ] s3
+      | s3 =  [ &_29 <- right_val ] s4
+      | s4 = {false} any ]
+       ]
+    )
+    [ & _0 : () = any_l ()
+    | & a : t_Filter'0 = any_l ()
+    | & _2 : t_Iter'0 = any_l ()
+    | & _6 : () = any_l ()
+    | & _8 : (t_Option'0, t_Option'0) = any_l ()
+    | & _10 : t_Option'0 = any_l ()
+    | & _11 : borrowed (t_Filter'0) = any_l ()
+    | & _12 : borrowed (t_Filter'0) = any_l ()
+    | & left_val : t_Option'0 = any_l ()
+    | & right_val : t_Option'0 = any_l ()
+    | & _19 : bool = any_l ()
+    | & kind : t_AssertKind'0 = any_l ()
+    | & _27 : t_Option'0 = any_l ()
+    | & _29 : t_Option'0 = any_l ()
+    | & _32 : (t_Option'0, t_Option'0) = any_l ()
+    | & _34 : t_Option'0 = any_l ()
+    | & _35 : borrowed (t_Filter'0) = any_l ()
+    | & _36 : borrowed (t_Filter'0) = any_l ()
+    | & left_val1 : t_Option'0 = any_l ()
+    | & right_val1 : t_Option'0 = any_l ()
+    | & _43 : bool = any_l ()
+    | & kind1 : t_AssertKind'0 = any_l ()
+    | & _51 : t_Option'0 = any_l ()
+    | & _53 : t_Option'0 = any_l ()
+    | & _56 : (t_Option'0, t_Option'0) = any_l ()
+    | & _58 : t_Option'0 = any_l ()
+    | & _59 : borrowed (t_Filter'0) = any_l ()
+    | & _60 : borrowed (t_Filter'0) = any_l ()
+    | & left_val2 : t_Option'0 = any_l ()
+    | & right_val2 : t_Option'0 = any_l ()
+    | & _65 : bool = any_l ()
+    | & kind2 : t_AssertKind'0 = any_l ()
+    | & _73 : t_Option'0 = any_l ()
+    | & _75 : t_Option'0 = any_l ()
+    | & _77 : t_Option'0 = any_l ()
+    | & _78 : t_Option'0 = any_l ()
+    | & _79 : t_Option'0 = any_l ()
+    | & _80 : array bool = any_l () ]
+     [ return' (result:())-> (! return' {result}) ] 
+end
+module M_iter__test_filter_map [#"iter.rs" 21 0 21 24]
+  let%span siter0 = "iter.rs" 22 17 22 21
+  let%span siter1 = "iter.rs" 22 23 22 28
+  let%span siter2 = "iter.rs" 22 30 22 34
+  let%span sslice3 = "../../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
+  let%span siter4 = "iter.rs" 24 32 24 37
+  let%span siter5 = "iter.rs" 23 18 23 63
+  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 183 27 183 51
+  let%span siter7 = "../../../../creusot-contracts/src/std/iter.rs" 184 27 184 57
+  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 185 27 185 49
+  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
+  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
+  let%span siter11 = "iter.rs" 26 37 26 42
+  let%span soption12 = "../../../../creusot-contracts/src/std/option.rs" 23 26 23 75
+  let%span siter13 = "iter.rs" 27 37 27 42
+  let%span sfilter_map14 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 56 16 56 52
+  let%span sfilter_map15 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 48 16 48 50
+  let%span sfilter_map16 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 63 16 63 135
+  let%span sfilter_map17 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 15 14 15 39
+  let%span sfilter_map18 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 22 14 22 39
+  let%span sfilter_map19 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 75 12 77 47
+  let%span sfilter_map20 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 85 12 98 148
+  let%span sresolve21 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
+  let%span smodel22 = "../../../../creusot-contracts/src/model.rs" 83 8 83 28
+  let%span sops23 = "../../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
+  let%span sops24 = "../../../../creusot-contracts/src/std/ops.rs" 110 14 110 36
+  let%span sops25 = "../../../../creusot-contracts/src/std/ops.rs" 115 14 115 31
+  let%span sops26 = "../../../../creusot-contracts/src/std/ops.rs" 120 15 120 29
+  let%span sops27 = "../../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
+  let%span sops28 = "../../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
+  let%span sops29 = "../../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
+  let%span sfilter_map30 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 104 14 104 45
+  let%span sfilter_map31 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 109 15 109 32
+  let%span sfilter_map32 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 110 15 110 32
+  let%span sfilter_map33 = "../../../../creusot-contracts/src/std/iter/filter_map.rs" 111 14 111 42
+  let%span sslice34 = "../../../../creusot-contracts/src/std/slice.rs" 405 12 405 66
+  let%span sslice35 = "../../../../creusot-contracts/src/std/slice.rs" 398 20 398 61
+  let%span sinvariant36 = "../../../../creusot-contracts/src/invariant.rs" 34 20 34 44
+  let%span soption37 = "../../../../creusot-contracts/src/std/option.rs" 11 8 14 9
+  let%span sslice38 = "../../../../creusot-contracts/src/std/slice.rs" 411 14 411 45
+  let%span sslice39 = "../../../../creusot-contracts/src/std/slice.rs" 409 4 409 10
+  let%span sslice40 = "../../../../creusot-contracts/src/std/slice.rs" 416 15 416 32
+  let%span sslice41 = "../../../../creusot-contracts/src/std/slice.rs" 417 15 417 32
+  let%span sslice42 = "../../../../creusot-contracts/src/std/slice.rs" 418 14 418 42
+  let%span sslice43 = "../../../../creusot-contracts/src/std/slice.rs" 414 4 414 10
+  let%span sslice44 = "../../../../creusot-contracts/src/std/slice.rs" 96 14 96 41
+  let%span sslice45 = "../../../../creusot-contracts/src/std/slice.rs" 97 14 97 80
+  let%span smodel46 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
+  let%span sslice47 = "../../../../creusot-contracts/src/std/slice.rs" 28 14 28 41
+  let%span sslice48 = "../../../../creusot-contracts/src/std/slice.rs" 29 14 29 42
+  let%span smodel49 = "../../../../creusot-contracts/src/model.rs" 120 8 120 12
+  let%span smodel50 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
+  let%span sindex51 = "../../../../creusot-contracts/src/logic/ops/index.rs" 49 8 49 31
+  
+  use prelude.prelude.Slice
+  
+  use prelude.prelude.Borrow
+  
+  use prelude.prelude.Intrinsic
+  
+  let rec promoted3__test_filter_map'0 (return'  (ret:array bool))= bb0
+    [ bb0 = s0
+      [ s0 = any
+        [ any_ (__arr_temp:array bool)-> (! -{Seq.get __arr_temp.elts 0
+          /\ Seq.get __arr_temp.elts 1 = ([%#siter1] false)
+          /\ Seq.get __arr_temp.elts 2 /\ Seq.length __arr_temp.elts = 3}-
+           [ &_1 <- __arr_temp ] 
+          s1) ]
+        
+      | s1 =  [ &_0 <- _1 ] s2
+      | s2 = return' {_0} ]
+       ]
+     [ & _0 : array bool = any_l () | & _1 : array bool = any_l () ] 
+    [ return' (result:array bool)-> return' {result} ]
+    
+  
+  predicate inv'2 (_1 : slice bool)
+  
+  axiom inv_axiom'2 [@rewrite] : forall x : slice bool [inv'2 x] . inv'2 x = true
+  
+  use prelude.prelude.Opaque
+  
+  type t_NonNull'0  =
+    { t_NonNull__pointer'0: opaque_ptr }
+  
+  type t_Iter'0  =
+    { t_Iter__ptr'0: t_NonNull'0; t_Iter__end_or_len'0: opaque_ptr; t_Iter__qy95zmarker'0: () }
+  
+  function view'0 (self : t_Iter'0) : slice bool
+  
+  let rec iter'0 (self:slice bool) (return'  (ret:t_Iter'0))= {[@expl:iter 'self' type invariant] inv'2 self}
+    any [ return' (result:t_Iter'0)-> {[%#sslice3] view'0 result = self} (! return' {result}) ] 
+  
+  predicate resolve'3 (self : borrowed ()) =
+    [%#sresolve21] self.final = self.current
+  
+  predicate resolve'1 (_1 : borrowed ()) =
+    resolve'3 _1
+  
+  type t_Option'0  =
+    | C_None'0
+    | C_Some'0 bool
+  
+  predicate postcondition_once'0 (self : ()) (args : bool) (result : t_Option'0) =
+    [%#siter5] let (b) = args in result = (if b then C_Some'0 false else C_None'0)
+  
+  predicate resolve'4 (_1 : ()) =
+    true
+  
+  predicate unnest'0 (self : ()) (_2 : ()) =
+    true
+  
+  predicate postcondition_mut'0 (self : ()) (args : bool) (result_state : ()) (result : t_Option'0) =
+    (let (b) = args in result = (if b then C_Some'0 false else C_None'0)) /\ unnest'0 self result_state
+  
+  function fn_mut_once'0 (self : ()) (args : bool) (res : t_Option'0) : ()
+  
+  axiom fn_mut_once'0_spec : forall self : (), args : bool, res : t_Option'0 . [%#sops29] postcondition_once'0 self args res
+  = (exists res_state : () . postcondition_mut'0 self args res_state res /\ resolve'4 res_state)
+  
+  function unnest_trans'0 (self : ()) (b : ()) (c : ()) : ()
+  
+  axiom unnest_trans'0_spec : forall self : (), b : (), c : () . ([%#sops26] unnest'0 self b)
+   -> ([%#sops27] unnest'0 b c)  -> ([%#sops28] unnest'0 self c)
+  
+  function unnest_refl'0 (self : ()) : ()
+  
+  axiom unnest_refl'0_spec : forall self : () . [%#sops25] unnest'0 self self
+  
+  function postcondition_mut_unnest'0 (self : ()) (args : bool) (res_state : ()) (res : t_Option'0) : ()
+  
+  axiom postcondition_mut_unnest'0_spec : forall self : (), args : bool, res_state : (), res : t_Option'0 . ([%#sops23] postcondition_mut'0 self args res_state res)
+   -> ([%#sops24] unnest'0 self res_state)
+  
+  let rec closure0'0 (_1:borrowed ()) (b:bool) (return'  (ret:t_Option'0))= (! bb0
+    [ bb0 = s0 [ s0 = -{resolve'1 _1}- s1 | s1 = any [ br0 -> {b = false} (! bb2) | br1 -> {b} (! bb1) ]  ] 
+    | bb1 = s0 [ s0 =  [ &res <- C_Some'0 ([%#siter4] false) ] s1 | s1 = bb3 ] 
+    | bb2 = s0 [ s0 =  [ &res <- C_None'0 ] s1 | s1 = bb3 ] 
+    | bb3 = s0 [ s0 =  [ &_0 <- res ] s1 | s1 = return' {_0} ]  ]
+    ) [ & _0 : t_Option'0 = any_l () | & _1 : borrowed () = _1 | & b : bool = b | & res : t_Option'0 = any_l () ] 
+    [ return' (result:t_Option'0)-> {[@expl:closure ensures] [%#siter5] result
+      = (if b then C_Some'0 false else C_None'0)}
+      {[@expl:closure unnest] unnest'0 _1.current _1.final}
+      (! return' {result}) ]
+    
+  
+  predicate inv'3 (_1 : t_Iter'0)
+  
+  axiom inv_axiom'3 [@rewrite] : forall x : t_Iter'0 [inv'3 x] . inv'3 x = true
+  
+  predicate inv'4 (_1 : ())
+  
+  axiom inv_axiom'4 [@rewrite] : forall x : () [inv'4 x] . inv'4 x = true
+  
+  predicate immutable'0 (f : ()) =
+    [%#sfilter_map14] forall g : () . unnest'0 f g  -> f = g
+  
+  predicate precondition'0 (self : ()) (args : bool) =
+    let (b) = args in true
+  
+  predicate no_precondition'0 (f : ()) =
+    [%#sfilter_map15] forall i : bool . precondition'0 f (i)
+  
+  predicate precise'0 (f1 : ()) =
+    [%#sfilter_map16] forall f2 : (), i : bool . not ((exists b : bool . postcondition_mut'0 f1 (i) f2 (C_Some'0 b))
+    /\ postcondition_mut'0 f1 (i) f2 (C_None'0))
+  
+  type t_FilterMap'0  =
+    { t_FilterMap__iter'0: t_Iter'0; t_FilterMap__f'0: () }
+  
+  predicate invariant'0 (self : t_FilterMap'0)
+  
+  predicate inv'0 (_1 : t_FilterMap'0)
+  
+  axiom inv_axiom'0 [@rewrite] : forall x : t_FilterMap'0 [inv'0 x] . inv'0 x
+  = (invariant'0 x
+  /\ match x with
+    | {t_FilterMap__iter'0 = iter ; t_FilterMap__f'0 = f} -> true
+    end)
+  
+  function iter'1 (self : t_FilterMap'0) : t_Iter'0
+  
+  axiom iter'1_spec : forall self : t_FilterMap'0 . [%#sfilter_map17] inv'0 self  -> inv'3 (iter'1 self)
+  
+  function func'0 (self : t_FilterMap'0) : ()
+  
+  axiom func'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map18] inv'0 self  -> inv'4 (func'0 self)
+  
+  let rec filter_map'0 (self:t_Iter'0) (f:()) (return'  (ret:t_FilterMap'0))= {[@expl:filter_map 'self' type invariant] inv'3 self}
+    {[@expl:filter_map 'f' type invariant] inv'4 f}
+    {[@expl:filter_map requires #0] [%#siter6] immutable'0 f}
+    {[@expl:filter_map requires #1] [%#siter7] no_precondition'0 f}
+    {[@expl:filter_map requires #2] [%#siter8] precise'0 f}
+    any
+    [ return' (result:t_FilterMap'0)-> {inv'0 result}
+      {[%#siter9] iter'1 result = self /\ func'0 result = f}
+      (! return' {result}) ]
+    
+  
+  predicate invariant'1 (self : borrowed (t_FilterMap'0)) =
+    [%#sinvariant36] inv'0 self.current /\ inv'0 self.final
+  
+  predicate inv'1 (_1 : borrowed (t_FilterMap'0))
+  
+  axiom inv_axiom'1 [@rewrite] : forall x : borrowed (t_FilterMap'0) [inv'1 x] . inv'1 x = invariant'1 x
+  
+  predicate inv'5 (_1 : t_Option'0)
+  
+  axiom inv_axiom'5 [@rewrite] : forall x : t_Option'0 [inv'5 x] . inv'5 x = true
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use prelude.prelude.Int
+  
+  use map.Map
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  use prelude.prelude.UIntSize
+  
+  constant v_MAX'0 : usize = (18446744073709551615 : usize)
+  
+  use prelude.prelude.UIntSize
+  
+  use prelude.prelude.Slice
+  
+  function view'2 (self : slice bool) : Seq.seq bool
+  
+  axiom view'2_spec : forall self : slice bool . ([%#sslice47] Seq.length (view'2 self)
+  <= UIntSize.to_int (v_MAX'0 : usize))
+  && ([%#sslice48] view'2 self = Slice.id self)
+  
+  function view'3 (self : slice bool) : Seq.seq bool =
+    [%#smodel50] view'2 self
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  function index_logic'0 [@inline:trivial] (self : slice bool) (ix : int) : bool =
+    [%#sindex51] Seq.get (view'2 self) ix
+  
+  function to_ref_seq'0 (self : slice bool) : Seq.seq bool
+  
+  axiom to_ref_seq'0_spec : forall self : slice bool . ([%#sslice44] Seq.length (to_ref_seq'0 self)
+  = Seq.length (view'3 self))
+  && ([%#sslice45] forall i : int . 0 <= i /\ i < Seq.length (to_ref_seq'0 self)
+   -> Seq.get (to_ref_seq'0 self) i = index_logic'0 self i)
+  
+  predicate produces'1 (self : t_Iter'0) (visited : Seq.seq bool) (tl : t_Iter'0) =
+    [%#sslice34] to_ref_seq'0 (view'0 self) = Seq.(++) visited (to_ref_seq'0 (view'0 tl))
+  
+  function produces_trans'1 (a : t_Iter'0) (ab : Seq.seq bool) (b : t_Iter'0) (bc : Seq.seq bool) (c : t_Iter'0) : () =
+    [%#sslice43] ()
+  
+  axiom produces_trans'1_spec : forall a : t_Iter'0, ab : Seq.seq bool, b : t_Iter'0, bc : Seq.seq bool, c : t_Iter'0 . ([%#sslice40] produces'1 a ab b)
+   -> ([%#sslice41] produces'1 b bc c)  -> ([%#sslice42] produces'1 a (Seq.(++) ab bc) c)
+  
+  function produces_refl'1 (self : t_Iter'0) : () =
+    [%#sslice39] ()
+  
+  axiom produces_refl'1_spec : forall self : t_Iter'0 . [%#sslice38] produces'1 self (Seq.empty  : Seq.seq bool) self
+  
+  use map.Map
+  
+  use seq.Seq
+  
+  use seq.Seq
+  
+  predicate produces'0 (self : t_FilterMap'0) (visited : Seq.seq bool) (succ : t_FilterMap'0) =
+    [%#sfilter_map20] invariant'0 self
+     -> unnest'0 (func'0 self) (func'0 succ)
+    /\ (exists s : Seq.seq bool, f : Map.map int int . produces'1 (iter'1 self) s (iter'1 succ)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited
+     -> postcondition_mut'0 (func'0 self) (Seq.get s (Map.get f i)) (func'0 self) (C_Some'0 (Seq.get visited i)))
+    /\ (forall j : int . 0 <= j /\ j < Seq.length s
+     -> (not (exists i : int . 0 <= i /\ i < Seq.length visited /\ Map.get f i = j))
+    = postcondition_mut'0 (func'0 self) (Seq.get s j) (func'0 self) (C_None'0)))
+  
+  function produces_trans'0 (a : t_FilterMap'0) (ab : Seq.seq bool) (b : t_FilterMap'0) (bc : Seq.seq bool) (c : t_FilterMap'0) : ()
+    
+  
+  axiom produces_trans'0_spec : forall a : t_FilterMap'0, ab : Seq.seq bool, b : t_FilterMap'0, bc : Seq.seq bool, c : t_FilterMap'0 . ([%#sfilter_map31] produces'0 a ab b)
+   -> ([%#sfilter_map32] produces'0 b bc c)  -> ([%#sfilter_map33] produces'0 a (Seq.(++) ab bc) c)
+  
+  function produces_refl'0 (self : t_FilterMap'0) : ()
+  
+  axiom produces_refl'0_spec : forall self : t_FilterMap'0 . [%#sfilter_map30] produces'0 self (Seq.empty  : Seq.seq bool) self
+  
+  predicate resolve'5 (self : borrowed (t_Iter'0)) =
+    [%#sresolve21] self.final = self.current
+  
+  function view'1 (self : borrowed (t_Iter'0)) : slice bool =
+    [%#smodel46] view'0 self.current
+  
+  predicate completed'1 (self : borrowed (t_Iter'0)) =
+    [%#sslice35] resolve'5 self /\ view'2 (view'1 self) = (Seq.empty  : Seq.seq bool)
+  
+  predicate completed'0 (self : borrowed (t_FilterMap'0)) =
+    [%#sfilter_map19] (exists s : Seq.seq bool, e : borrowed (t_Iter'0) . produces'1 (iter'1 self.current) s e.current
+    /\ completed'1 e
+    /\ (forall i : int . 0 <= i /\ i < Seq.length s
+     -> postcondition_mut'0 (func'0 self.current) (Seq.get s i) (func'0 self.final) (C_None'0)))
+    /\ func'0 self.current = func'0 self.final
+  
+  use seq.Seq
+  
+  let rec next'0 (self:borrowed (t_FilterMap'0)) (return'  (ret:t_Option'0))= {[@expl:next 'self' type invariant] inv'1 self}
+    any
+    [ return' (result:t_Option'0)-> {inv'5 result}
+      {[%#siter10] match result with
+        | C_None'0 -> completed'0 self
+        | C_Some'0 v -> produces'0 self.current (Seq.singleton v) self.final
+        end}
+      (! return' {result}) ]
+    
+  
+  predicate resolve'2 (self : borrowed (t_FilterMap'0)) =
+    [%#sresolve21] self.final = self.current
+  
+  predicate resolve'0 (_1 : borrowed (t_FilterMap'0)) =
+    resolve'2 _1
+  
+  let rec promoted2__test_filter_map'0 (return'  (ret:t_Option'0))= bb0
+    [ bb0 = s0 [ s0 =  [ &_1 <- C_Some'0 ([%#siter11] false) ] s1 | s1 =  [ &_0 <- _1 ] s2 | s2 = return' {_0} ]  ]
+     [ & _0 : t_Option'0 = any_l () | & _1 : t_Option'0 = any_l () ] 
+    [ return' (result:t_Option'0)-> return' {result} ]
+    
+  
+  predicate inv'6 (_1 : t_Option'0)
+  
+  axiom inv_axiom'6 [@rewrite] : forall x : t_Option'0 [inv'6 x] . inv'6 x = true
+  
+  function deep_model'2 (self : bool) : bool =
+    [%#smodel49] self
+  
+  function deep_model'1 (self : t_Option'0) : t_Option'0 =
+    [%#soption37] match self with
+      | C_Some'0 t -> C_Some'0 (deep_model'2 t)
+      | C_None'0 -> C_None'0
+      end
+  
+  function deep_model'0 (self : t_Option'0) : t_Option'0 =
+    [%#smodel22] deep_model'1 self
+  
+  let rec eq'0 (self:t_Option'0) (other:t_Option'0) (return'  (ret:bool))= {[@expl:eq 'self' type invariant] inv'6 self}
+    {[@expl:eq 'other' type invariant] inv'6 other}
+    any
+    [ return' (result:bool)-> {[%#soption12] result = (deep_model'0 self = deep_model'0 other)} (! return' {result}) ]
+    
+  
+  let rec promoted1__test_filter_map'0 (return'  (ret:t_Option'0))= bb0
+    [ bb0 = s0 [ s0 =  [ &_1 <- C_Some'0 ([%#siter13] false) ] s1 | s1 =  [ &_0 <- _1 ] s2 | s2 = return' {_0} ]  ]
+     [ & _0 : t_Option'0 = any_l () | & _1 : t_Option'0 = any_l () ] 
+    [ return' (result:t_Option'0)-> return' {result} ]
+    
+  
+  let rec promoted0__test_filter_map'0 (return'  (ret:t_Option'0))= bb0
+    [ bb0 = s0 [ s0 =  [ &_1 <- C_None'0 ] s1 | s1 =  [ &_0 <- _1 ] s2 | s2 = return' {_0} ]  ]
+     [ & _0 : t_Option'0 = any_l () | & _1 : t_Option'0 = any_l () ] 
+    [ return' (result:t_Option'0)-> return' {result} ]
+    
+  
+  type t_AssertKind'0  =
+    | C_Eq'0
+    | C_Ne'0
+    | C_Match'0
+  
+  meta "compute_max_steps" 1000000
+  
+  let rec test_filter_map'0 (_1:()) (return'  (ret:()))= (! bb0
+    [ bb0 = s0
+      [ s0 = promoted3__test_filter_map'0 (fun (pr3:array bool) ->  [ &_76 <- pr3 ] s1)
+      | s1 = iter'0 {_76} (fun (_ret':t_Iter'0) ->  [ &_2 <- _ret' ] s2)
+      | s2 = bb1 ]
+      
+    | bb1 = s0
+      [ s0 =  [ &_6 <- () ] s1
+      | s1 = filter_map'0 {_2} {_6} (fun (_ret':t_FilterMap'0) ->  [ &a <- _ret' ] s2)
+      | s2 = bb2 ]
+      
+    | bb2 = s0
+      [ s0 = {inv'0 a}
+        Borrow.borrow_mut <t_FilterMap'0> {a}
+          (fun (_ret':borrowed (t_FilterMap'0)) ->  [ &_12 <- _ret' ] -{inv'0 _ret'.final}-  [ &a <- _ret'.final ] s1)
+      | s1 = {inv'0 _12.current}
+        Borrow.borrow_final <t_FilterMap'0> {_12.current} {Borrow.get_id _12}
+          (fun (_ret':borrowed (t_FilterMap'0)) ->
+             [ &_11 <- _ret' ] 
+            -{inv'0 _ret'.final}-
+             [ &_12 <- { _12 with current = _ret'.final } ] 
+            s2)
+      | s2 = next'0 {_11} (fun (_ret':t_Option'0) ->  [ &_10 <- _ret' ] s3)
+      | s3 = bb3 ]
+      
+    | bb3 = s0
+      [ s0 = {[@expl:type invariant] inv'1 _12} s1
+      | s1 = -{resolve'0 _12}- s2
+      | s2 = promoted2__test_filter_map'0 (fun (pr2:t_Option'0) ->  [ &_75 <- pr2 ] s3)
+      | s3 =  [ &_8 <- (_10, _75) ] s4
+      | s4 =  [ &left_val <- let (r'0, _) = _8 in r'0 ] s5
+      | s5 =  [ &right_val <- let (_, r'1) = _8 in r'1 ] s6
+      | s6 = eq'0 {left_val} {right_val} (fun (_ret':bool) ->  [ &_17 <- _ret' ] s7)
+      | s7 = bb4 ]
+      
+    | bb4 = any [ br0 -> {_17 = false} (! bb6) | br1 -> {_17} (! bb5) ] 
+    | bb5 = s0
+      [ s0 = {inv'0 a}
+        Borrow.borrow_mut <t_FilterMap'0> {a}
+          (fun (_ret':borrowed (t_FilterMap'0)) ->  [ &_34 <- _ret' ] -{inv'0 _ret'.final}-  [ &a <- _ret'.final ] s1)
+      | s1 = {inv'0 _34.current}
+        Borrow.borrow_final <t_FilterMap'0> {_34.current} {Borrow.get_id _34}
+          (fun (_ret':borrowed (t_FilterMap'0)) ->
+             [ &_33 <- _ret' ] 
+            -{inv'0 _ret'.final}-
+             [ &_34 <- { _34 with current = _ret'.final } ] 
+            s2)
+      | s2 = next'0 {_33} (fun (_ret':t_Option'0) ->  [ &_32 <- _ret' ] s3)
+      | s3 = bb7 ]
+      
+    | bb7 = s0
+      [ s0 = {[@expl:type invariant] inv'1 _34} s1
+      | s1 = -{resolve'0 _34}- s2
+      | s2 = promoted1__test_filter_map'0 (fun (pr1:t_Option'0) ->  [ &_74 <- pr1 ] s3)
+      | s3 =  [ &_30 <- (_32, _74) ] s4
+      | s4 =  [ &left_val1 <- let (r'0, _) = _30 in r'0 ] s5
+      | s5 =  [ &right_val1 <- let (_, r'1) = _30 in r'1 ] s6
+      | s6 = eq'0 {left_val1} {right_val1} (fun (_ret':bool) ->  [ &_39 <- _ret' ] s7)
+      | s7 = bb8 ]
+      
+    | bb8 = any [ br0 -> {_39 = false} (! bb10) | br1 -> {_39} (! bb9) ] 
+    | bb9 = s0
+      [ s0 = {inv'0 a}
+        Borrow.borrow_mut <t_FilterMap'0> {a}
+          (fun (_ret':borrowed (t_FilterMap'0)) ->  [ &_56 <- _ret' ] -{inv'0 _ret'.final}-  [ &a <- _ret'.final ] s1)
+      | s1 = {inv'0 _56.current}
+        Borrow.borrow_final <t_FilterMap'0> {_56.current} {Borrow.get_id _56}
+          (fun (_ret':borrowed (t_FilterMap'0)) ->
+             [ &_55 <- _ret' ] 
+            -{inv'0 _ret'.final}-
+             [ &_56 <- { _56 with current = _ret'.final } ] 
+            s2)
+      | s2 = next'0 {_55} (fun (_ret':t_Option'0) ->  [ &_54 <- _ret' ] s3)
+      | s3 = bb11 ]
+      
+    | bb11 = s0
+      [ s0 = {[@expl:type invariant] inv'1 _56} s1
+      | s1 = -{resolve'0 _56}- s2
+      | s2 = {[@expl:type invariant] inv'0 a} s3
+      | s3 = promoted0__test_filter_map'0 (fun (pr0:t_Option'0) ->  [ &_73 <- pr0 ] s4)
+      | s4 =  [ &_52 <- (_54, _73) ] s5
+      | s5 =  [ &left_val2 <- let (r'0, _) = _52 in r'0 ] s6
+      | s6 =  [ &right_val2 <- let (_, r'1) = _52 in r'1 ] s7
+      | s7 = eq'0 {left_val2} {right_val2} (fun (_ret':bool) ->  [ &_61 <- _ret' ] s8)
+      | s8 = bb12 ]
+      
+    | bb12 = any [ br0 -> {_61 = false} (! bb14) | br1 -> {_61} (! bb13) ] 
+    | bb13 = return' {_0}
+    | bb14 = s0
+      [ s0 =  [ &kind2 <- C_Eq'0 ] s1
+      | s1 =  [ &_69 <- left_val2 ] s2
+      | s2 =  [ &_71 <- right_val2 ] s3
+      | s3 = {false} any ]
+      
+    | bb10 = s0
+      [ s0 = {[@expl:type invariant] inv'0 a} s1
+      | s1 =  [ &kind1 <- C_Eq'0 ] s2
+      | s2 =  [ &_47 <- left_val1 ] s3
+      | s3 =  [ &_49 <- right_val1 ] s4
+      | s4 = {false} any ]
+      
+    | bb6 = s0
+      [ s0 = {[@expl:type invariant] inv'0 a} s1
+      | s1 =  [ &kind <- C_Eq'0 ] s2
+      | s2 =  [ &_25 <- left_val ] s3
+      | s3 =  [ &_27 <- right_val ] s4
+      | s4 = {false} any ]
+       ]
+    )
+    [ & _0 : () = any_l ()
+    | & a : t_FilterMap'0 = any_l ()
+    | & _2 : t_Iter'0 = any_l ()
+    | & _6 : () = any_l ()
+    | & _8 : (t_Option'0, t_Option'0) = any_l ()
+    | & _10 : t_Option'0 = any_l ()
+    | & _11 : borrowed (t_FilterMap'0) = any_l ()
+    | & _12 : borrowed (t_FilterMap'0) = any_l ()
+    | & left_val : t_Option'0 = any_l ()
+    | & right_val : t_Option'0 = any_l ()
+    | & _17 : bool = any_l ()
+    | & kind : t_AssertKind'0 = any_l ()
+    | & _25 : t_Option'0 = any_l ()
+    | & _27 : t_Option'0 = any_l ()
+    | & _30 : (t_Option'0, t_Option'0) = any_l ()
+    | & _32 : t_Option'0 = any_l ()
+    | & _33 : borrowed (t_FilterMap'0) = any_l ()
+    | & _34 : borrowed (t_FilterMap'0) = any_l ()
+    | & left_val1 : t_Option'0 = any_l ()
+    | & right_val1 : t_Option'0 = any_l ()
+    | & _39 : bool = any_l ()
+    | & kind1 : t_AssertKind'0 = any_l ()
+    | & _47 : t_Option'0 = any_l ()
+    | & _49 : t_Option'0 = any_l ()
+    | & _52 : (t_Option'0, t_Option'0) = any_l ()
+    | & _54 : t_Option'0 = any_l ()
+    | & _55 : borrowed (t_FilterMap'0) = any_l ()
+    | & _56 : borrowed (t_FilterMap'0) = any_l ()
+    | & left_val2 : t_Option'0 = any_l ()
+    | & right_val2 : t_Option'0 = any_l ()
+    | & _61 : bool = any_l ()
+    | & kind2 : t_AssertKind'0 = any_l ()
+    | & _69 : t_Option'0 = any_l ()
+    | & _71 : t_Option'0 = any_l ()
+    | & _73 : t_Option'0 = any_l ()
+    | & _74 : t_Option'0 = any_l ()
+    | & _75 : t_Option'0 = any_l ()
+    | & _76 : array bool = any_l () ]
+     [ return' (result:())-> (! return' {result}) ] 
+end
diff --git a/creusot/tests/should_succeed/cc/iter.rs b/creusot/tests/should_succeed/cc/iter.rs
index a74861d6f..c1c521874 100644
--- a/creusot/tests/should_succeed/cc/iter.rs
+++ b/creusot/tests/should_succeed/cc/iter.rs
@@ -1,4 +1,5 @@
 extern crate creusot_contracts;
+use creusot_contracts::*;
 
 pub fn test_mut_ref() {
     let mut a = [1, 2].iter();
@@ -6,3 +7,23 @@ pub fn test_mut_ref() {
     assert_eq!((&mut a).next(), Some(&2));
     assert_eq!((&mut a).next(), None);
 }
+
+pub fn test_filter() {
+    let mut a = [true, false, true].iter().filter(
+        #[ensures(result == **b)]
+        |b: &&bool| **b,
+    );
+    assert_eq!((&mut a).next(), Some(&true));
+    assert_eq!((&mut a).next(), Some(&true));
+    assert_eq!((&mut a).next(), None);
+}
+
+pub fn test_filter_map() {
+    let mut a = [true, false, true].iter().filter_map(
+        #[ensures(result == if *b { Some(false) } else { None })]
+        |b: &bool| if *b { Some(false) } else { None },
+    );
+    assert_eq!((&mut a).next(), Some(false));
+    assert_eq!((&mut a).next(), Some(false));
+    assert_eq!((&mut a).next(), None);
+}
diff --git a/creusot/tests/should_succeed/cc/iter/why3session.xml b/creusot/tests/should_succeed/cc/iter/why3session.xml
index 64f15028f..8cf5e5320 100644
--- a/creusot/tests/should_succeed/cc/iter/why3session.xml
+++ b/creusot/tests/should_succeed/cc/iter/why3session.xml
@@ -3,6 +3,9 @@
 "https://www.why3.org/why3session.dtd">
 <why3session shape_version="6">
 <prover id="0" name="Z3" version="4.12.4" timelimit="5" steplimit="0" memlimit="1000"/>
+<prover id="1" name="CVC4" version="1.8" timelimit="5" steplimit="0" memlimit="1000"/>
+<prover id="2" name="CVC5" version="1.0.5" timelimit="5" steplimit="0" memlimit="1000"/>
+<prover id="3" name="Alt-Ergo" version="2.6.0" timelimit="5" steplimit="0" memlimit="1000"/>
 <file format="coma" proved="true">
 <path name=".."/><path name="iter.coma"/>
 <theory name="M_iter__test_mut_ref" proved="true">
@@ -10,5 +13,219 @@
  <proof prover="0"><result status="valid" time="0.151632" steps="189794"/></proof>
  </goal>
 </theory>
+<theory name="M_iter__test_filter" proved="true">
+ <goal name="vc_closure0&#39;0" proved="true">
+ <proof prover="3"><result status="valid" time="0.020909" steps="0"/></proof>
+ </goal>
+ <goal name="vc_test_filter&#39;0" proved="true">
+ <transf name="split_vc" proved="true" >
+  <goal name="vc_test_filter&#39;0.0" expl="iter &#39;self&#39; type invariant" proved="true">
+  <proof prover="2"><result status="valid" time="0.032125" steps="5214"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.1" expl="filter &#39;self&#39; type invariant" proved="true">
+  <proof prover="0"><result status="valid" time="0.018751" steps="36788"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.2" expl="filter &#39;predicate&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.021587" steps="16"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.3" expl="filter requires #0" proved="true">
+  <proof prover="2"><result status="valid" time="0.034917" steps="7832"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.4" expl="filter requires #1" proved="true">
+  <proof prover="3"><result status="valid" time="0.024716" steps="32"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.5" expl="filter requires #2" proved="true">
+  <proof prover="3"><result status="valid" time="0.011760" steps="38"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.6" proved="true">
+  <proof prover="3"><result status="valid" time="0.031778" steps="18"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.7" proved="true">
+  <proof prover="2"><result status="valid" time="0.033871" steps="4500"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.8" expl="next &#39;self&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.020184" steps="27"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.9" expl="type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.022937" steps="27"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.10" expl="eq &#39;self&#39; type invariant" proved="true">
+  <proof prover="1"><result status="valid" time="0.041595" steps="9905"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.11" expl="eq &#39;other&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.016785" steps="33"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.12" proved="true">
+  <transf name="destruct_term" proved="true" arg1="result1">
+   <goal name="vc_test_filter&#39;0.12.0" proved="true">
+   <proof prover="1"><result status="valid" time="0.091239" steps="19243"/></proof>
+   </goal>
+   <goal name="vc_test_filter&#39;0.12.1" proved="true">
+   <proof prover="3"><result status="valid" time="0.033330" steps="300"/></proof>
+   </goal>
+  </transf>
+  </goal>
+  <goal name="vc_test_filter&#39;0.13" proved="true">
+  <proof prover="1"><result status="valid" time="0.029132" steps="10088"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.14" proved="true">
+  <proof prover="3"><result status="valid" time="0.018306" steps="36"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.15" expl="next &#39;self&#39; type invariant" proved="true">
+  <proof prover="1"><result status="valid" time="0.036864" steps="11819"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.16" expl="type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.036962" steps="47"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.17" expl="eq &#39;self&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.025998" steps="48"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.18" expl="eq &#39;other&#39; type invariant" proved="true">
+  <proof prover="2"><result status="valid" time="0.052712" steps="6991"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.19" proved="true">
+  <transf name="destruct_term" proved="true" arg1="result1">
+   <goal name="vc_test_filter&#39;0.19.0" proved="true">
+   <proof prover="1"><result status="valid" time="0.082272" steps="22615"/></proof>
+   </goal>
+   <goal name="vc_test_filter&#39;0.19.1" proved="true">
+   <proof prover="3"><result status="valid" time="0.629774" steps="9515"/></proof>
+   </goal>
+  </transf>
+  </goal>
+  <goal name="vc_test_filter&#39;0.20" proved="true">
+  <proof prover="3"><result status="valid" time="0.008201" steps="48"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.21" proved="true">
+  <proof prover="3"><result status="valid" time="0.017685" steps="50"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.22" expl="next &#39;self&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.032500" steps="65"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.23" expl="type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.044800" steps="64"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.24" expl="type invariant" proved="true">
+  <proof prover="0"><result status="valid" time="0.018386" steps="3718"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.25" expl="eq &#39;self&#39; type invariant" proved="true">
+  <proof prover="0"><result status="valid" time="0.034461" steps="51786"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.26" expl="eq &#39;other&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.031602" steps="65"/></proof>
+  </goal>
+  <goal name="vc_test_filter&#39;0.27" proved="true">
+  <proof prover="0"><result status="valid" time="2.827868" steps="3242375"/></proof>
+  </goal>
+ </transf>
+ </goal>
+</theory>
+<theory name="M_iter__test_filter_map" proved="true">
+ <goal name="vc_closure0&#39;0" proved="true">
+ <proof prover="3"><result status="valid" time="0.017222" steps="2"/></proof>
+ </goal>
+ <goal name="vc_test_filter_map&#39;0" proved="true">
+ <transf name="split_vc" proved="true" >
+  <goal name="vc_test_filter_map&#39;0.0" expl="iter &#39;self&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.054495" steps="12"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.1" expl="filter_map &#39;self&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.062727" steps="14"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.2" expl="filter_map &#39;f&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.049625" steps="16"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.3" expl="filter_map requires #0" proved="true">
+  <proof prover="0"><result status="valid" time="0.063640" steps="36918"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.4" expl="filter_map requires #1" proved="true">
+  <proof prover="2"><result status="valid" time="0.030610" steps="7968"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.5" expl="filter_map requires #2" proved="true">
+  <proof prover="2"><result status="valid" time="0.036794" steps="8899"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.6" proved="true">
+  <proof prover="3"><result status="valid" time="0.008663" steps="18"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.7" proved="true">
+  <proof prover="0"><result status="valid" time="0.016243" steps="2907"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.8" expl="next &#39;self&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.008903" steps="27"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.9" expl="type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.009617" steps="27"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.10" expl="eq &#39;self&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.058639" steps="31"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.11" expl="eq &#39;other&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.024634" steps="33"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.12" proved="true">
+  <transf name="destruct_term" proved="true" arg1="result1">
+   <goal name="vc_test_filter_map&#39;0.12.0" proved="true">
+   <proof prover="0"><result status="valid" time="0.034254" steps="59131"/></proof>
+   </goal>
+   <goal name="vc_test_filter_map&#39;0.12.1" proved="true">
+   <proof prover="3"><result status="valid" time="0.030693" steps="289"/></proof>
+   </goal>
+  </transf>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.13" proved="true">
+  <proof prover="1"><result status="valid" time="0.054029" steps="9654"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.14" proved="true">
+  <proof prover="0"><result status="valid" time="0.031234" steps="3524"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.15" expl="next &#39;self&#39; type invariant" proved="true">
+  <proof prover="0"><result status="valid" time="0.027998" steps="50155"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.16" expl="type invariant" proved="true">
+  <proof prover="1"><result status="valid" time="0.060686" steps="11581"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.17" expl="eq &#39;self&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.011718" steps="46"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.18" expl="eq &#39;other&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.057591" steps="48"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.19" proved="true">
+  <transf name="destruct_term" proved="true" arg1="result1">
+   <goal name="vc_test_filter_map&#39;0.19.0" proved="true">
+   <proof prover="0"><result status="valid" time="0.030985" steps="64482"/></proof>
+   </goal>
+   <goal name="vc_test_filter_map&#39;0.19.1" proved="true">
+   <proof prover="3"><result status="valid" time="1.530085" steps="21394"/></proof>
+   </goal>
+  </transf>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.20" proved="true">
+  <proof prover="2"><result status="valid" time="0.032861" steps="5380"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.21" proved="true">
+  <proof prover="2"><result status="valid" time="0.026590" steps="5385"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.22" expl="next &#39;self&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.018084" steps="62"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.23" expl="type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.024264" steps="62"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.24" expl="type invariant" proved="true">
+  <proof prover="2"><result status="valid" time="0.018554" steps="5487"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.25" expl="eq &#39;self&#39; type invariant" proved="true">
+  <proof prover="1"><result status="valid" time="0.039864" steps="10394"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.26" expl="eq &#39;other&#39; type invariant" proved="true">
+  <proof prover="3"><result status="valid" time="0.032055" steps="63"/></proof>
+  </goal>
+  <goal name="vc_test_filter_map&#39;0.27" proved="true">
+  <proof prover="0"><result status="valid" time="0.811406" steps="1906353"/></proof>
+  </goal>
+ </transf>
+ </goal>
+</theory>
 </file>
 </why3session>
diff --git a/creusot/tests/should_succeed/cc/iter/why3shapes.gz b/creusot/tests/should_succeed/cc/iter/why3shapes.gz
index 4834e6dca..3ad65f939 100644
Binary files a/creusot/tests/should_succeed/cc/iter/why3shapes.gz and b/creusot/tests/should_succeed/cc/iter/why3shapes.gz differ
diff --git a/creusot/tests/should_succeed/ghost/ghost_set.coma b/creusot/tests/should_succeed/ghost/ghost_set.coma
index 715ebc53b..cc7b9fca1 100644
--- a/creusot/tests/should_succeed/ghost/ghost_set.coma
+++ b/creusot/tests/should_succeed/ghost/ghost_set.coma
@@ -1,7 +1,7 @@
 module M_ghost_set__ghost_map [#"ghost_set.rs" 4 0 4 18]
   let%span sghost_set0 = "ghost_set.rs" 5 18 5 36
-  let%span sfset1 = "../../../../creusot-contracts/src/logic/fset.rs" 196 4 196 34
-  let%span sfset2 = "../../../../creusot-contracts/src/logic/fset.rs" 194 14 194 31
+  let%span sfset1 = "../../../../creusot-contracts/src/logic/fset.rs" 316 4 316 34
+  let%span sfset2 = "../../../../creusot-contracts/src/logic/fset.rs" 314 14 314 31
   let%span sghost_set3 = "ghost_set.rs" 7 22 7 53
   let%span sghost_set4 = "ghost_set.rs" 8 25 8 26
   let%span sghost_set5 = "ghost_set.rs" 10 22 10 63
@@ -25,22 +25,22 @@ module M_ghost_set__ghost_map [#"ghost_set.rs" 4 0 4 18]
   let%span sghost23 = "../../../../creusot-contracts/src/ghost.rs" 85 22 85 26
   let%span sghost24 = "../../../../creusot-contracts/src/ghost.rs" 85 4 85 48
   let%span sghost25 = "../../../../creusot-contracts/src/ghost.rs" 84 14 84 36
-  let%span sfset26 = "../../../../creusot-contracts/src/logic/fset.rs" 277 29 277 33
-  let%span sfset27 = "../../../../creusot-contracts/src/logic/fset.rs" 277 35 277 40
-  let%span sfset28 = "../../../../creusot-contracts/src/logic/fset.rs" 275 14 275 44
-  let%span sfset29 = "../../../../creusot-contracts/src/logic/fset.rs" 276 14 276 48
+  let%span sfset26 = "../../../../creusot-contracts/src/logic/fset.rs" 397 29 397 33
+  let%span sfset27 = "../../../../creusot-contracts/src/logic/fset.rs" 397 35 397 40
+  let%span sfset28 = "../../../../creusot-contracts/src/logic/fset.rs" 395 14 395 44
+  let%span sfset29 = "../../../../creusot-contracts/src/logic/fset.rs" 396 14 396 48
   let%span sghost30 = "../../../../creusot-contracts/src/ghost.rs" 69 14 69 18
   let%span sghost31 = "../../../../creusot-contracts/src/ghost.rs" 69 4 69 36
   let%span sghost32 = "../../../../creusot-contracts/src/ghost.rs" 68 14 68 35
-  let%span sfset33 = "../../../../creusot-contracts/src/logic/fset.rs" 222 22 222 26
-  let%span sfset34 = "../../../../creusot-contracts/src/logic/fset.rs" 221 14 221 34
-  let%span sfset35 = "../../../../creusot-contracts/src/logic/fset.rs" 313 29 313 33
-  let%span sfset36 = "../../../../creusot-contracts/src/logic/fset.rs" 313 35 313 40
-  let%span sfset37 = "../../../../creusot-contracts/src/logic/fset.rs" 311 14 311 45
-  let%span sfset38 = "../../../../creusot-contracts/src/logic/fset.rs" 312 14 312 48
-  let%span sfset39 = "../../../../creusot-contracts/src/logic/fset.rs" 243 27 243 31
-  let%span sfset40 = "../../../../creusot-contracts/src/logic/fset.rs" 243 33 243 38
-  let%span sfset41 = "../../../../creusot-contracts/src/logic/fset.rs" 242 14 242 45
+  let%span sfset33 = "../../../../creusot-contracts/src/logic/fset.rs" 342 22 342 26
+  let%span sfset34 = "../../../../creusot-contracts/src/logic/fset.rs" 341 14 341 34
+  let%span sfset35 = "../../../../creusot-contracts/src/logic/fset.rs" 433 29 433 33
+  let%span sfset36 = "../../../../creusot-contracts/src/logic/fset.rs" 433 35 433 40
+  let%span sfset37 = "../../../../creusot-contracts/src/logic/fset.rs" 431 14 431 45
+  let%span sfset38 = "../../../../creusot-contracts/src/logic/fset.rs" 432 14 432 48
+  let%span sfset39 = "../../../../creusot-contracts/src/logic/fset.rs" 363 27 363 31
+  let%span sfset40 = "../../../../creusot-contracts/src/logic/fset.rs" 363 33 363 38
+  let%span sfset41 = "../../../../creusot-contracts/src/logic/fset.rs" 362 14 362 45
   let%span sghost42 = "../../../../creusot-contracts/src/ghost.rs" 181 15 181 16
   let%span sghost43 = "../../../../creusot-contracts/src/ghost.rs" 181 4 181 28
   let%span sghost44 = "../../../../creusot-contracts/src/ghost.rs" 179 14 179 28
diff --git a/creusot/tests/should_succeed/hillel.coma b/creusot/tests/should_succeed/hillel.coma
index 92d67b95c..8504d79b4 100644
--- a/creusot/tests/should_succeed/hillel.coma
+++ b/creusot/tests/should_succeed/hillel.coma
@@ -504,11 +504,11 @@ module M_hillel__insert_unique [#"hillel.rs" 80 0 80 62]
   let%span shillel22 = "hillel.rs" 67 8 67 72
   let%span svec23 = "../../../creusot-contracts/src/std/vec.rs" 169 26 169 42
   let%span sslice24 = "../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
-  let%span siter25 = "../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter25 = "../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span sindex26 = "../../../creusot-contracts/src/logic/ops/index.rs" 93 8 93 33
   let%span smodel27 = "../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span sslice28 = "../../../creusot-contracts/src/std/slice.rs" 405 12 405 66
-  let%span siter29 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter29 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span sindex30 = "../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
   let%span scmp31 = "../../../creusot-contracts/src/std/cmp.rs" 11 26 11 75
   let%span shillel32 = "hillel.rs" 60 8 60 64
@@ -517,8 +517,8 @@ module M_hillel__insert_unique [#"hillel.rs" 80 0 80 62]
   let%span svec35 = "../../../creusot-contracts/src/std/vec.rs" 29 14 29 47
   let%span svec36 = "../../../creusot-contracts/src/std/vec.rs" 30 14 31 51
   let%span smodel37 = "../../../creusot-contracts/src/model.rs" 92 8 92 22
-  let%span siter38 = "../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter39 = "../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter38 = "../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter39 = "../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span sslice40 = "../../../creusot-contracts/src/std/slice.rs" 411 14 411 45
   let%span sslice41 = "../../../creusot-contracts/src/std/slice.rs" 409 4 409 10
   let%span sslice42 = "../../../creusot-contracts/src/std/slice.rs" 416 15 416 32
@@ -1018,14 +1018,14 @@ module M_hillel__unique [#"hillel.rs" 102 0 102 56]
   let%span shillel19 = "hillel.rs" 101 10 101 58
   let%span svec20 = "../../../creusot-contracts/src/std/vec.rs" 74 26 74 44
   let%span sslice21 = "../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
-  let%span siter22 = "../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter22 = "../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span smodel23 = "../../../creusot-contracts/src/model.rs" 83 8 83 28
   let%span svec24 = "../../../creusot-contracts/src/std/vec.rs" 29 14 29 47
   let%span svec25 = "../../../creusot-contracts/src/std/vec.rs" 30 14 31 51
   let%span shillel26 = "hillel.rs" 67 8 67 72
   let%span shillel27 = "hillel.rs" 53 8 53 105
   let%span srange28 = "../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter29 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter29 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span shillel30 = "hillel.rs" 80 36 80 39
   let%span shillel31 = "hillel.rs" 80 54 80 58
   let%span shillel32 = "hillel.rs" 75 11 75 38
@@ -1035,8 +1035,8 @@ module M_hillel__unique [#"hillel.rs" 102 0 102 56]
   let%span shillel36 = "hillel.rs" 79 10 79 58
   let%span smodel37 = "../../../creusot-contracts/src/model.rs" 92 8 92 22
   let%span svec38 = "../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  let%span siter39 = "../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter40 = "../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter39 = "../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter40 = "../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span sslice41 = "../../../creusot-contracts/src/std/slice.rs" 40 14 40 44
   let%span sslice42 = "../../../creusot-contracts/src/std/slice.rs" 41 14 41 96
   let%span sindex43 = "../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
@@ -1670,14 +1670,14 @@ module M_hillel__fulcrum [#"hillel.rs" 159 0 159 30]
   let%span shillel22 = "hillel.rs" 156 11 156 23
   let%span shillel23 = "hillel.rs" 157 10 157 44
   let%span shillel24 = "hillel.rs" 158 10 158 86
-  let%span siter25 = "../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter25 = "../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span smodel26 = "../../../creusot-contracts/src/model.rs" 92 8 92 22
   let%span shillel27 = "hillel.rs" 123 11 123 53
   let%span shillel28 = "hillel.rs" 124 10 124 21
   let%span shillel29 = "hillel.rs" 122 10 122 19
   let%span shillel30 = "hillel.rs" 121 0 121 8
   let%span sslice31 = "../../../creusot-contracts/src/std/slice.rs" 405 12 405 66
-  let%span siter32 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter32 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span sslice33 = "../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
   let%span shillel34 = "hillel.rs" 144 11 144 35
   let%span shillel35 = "hillel.rs" 145 10 145 64
@@ -1699,8 +1699,8 @@ module M_hillel__fulcrum [#"hillel.rs" 159 0 159 30]
   let%span sslice51 = "../../../creusot-contracts/src/std/slice.rs" 97 14 97 80
   let%span sslice52 = "../../../creusot-contracts/src/std/slice.rs" 398 20 398 61
   let%span sresolve53 = "../../../creusot-contracts/src/resolve.rs" 54 20 54 34
-  let%span siter54 = "../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter55 = "../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter54 = "../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter55 = "../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span shillel56 = "hillel.rs" 135 11 135 63
   let%span shillel57 = "hillel.rs" 136 10 136 85
   let%span shillel58 = "hillel.rs" 134 10 134 18
diff --git a/creusot/tests/should_succeed/insertion_sort.coma b/creusot/tests/should_succeed/insertion_sort.coma
index 76c9889d8..26e29f517 100644
--- a/creusot/tests/should_succeed/insertion_sort.coma
+++ b/creusot/tests/should_succeed/insertion_sort.coma
@@ -23,13 +23,13 @@ module M_insertion_sort__insertion_sort [#"insertion_sort.rs" 21 0 21 40]
   let%span sinsertion_sort21 = "insertion_sort.rs" 19 10 19 42
   let%span sinsertion_sort22 = "insertion_sort.rs" 20 10 20 27
   let%span sslice23 = "../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
-  let%span siter24 = "../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter24 = "../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span ssnapshot25 = "../../../creusot-contracts/src/snapshot.rs" 52 20 52 39
   let%span smodel26 = "../../../creusot-contracts/src/model.rs" 110 8 110 22
   let%span sseq27 = "../../../creusot-contracts/src/logic/seq.rs" 316 8 316 41
   let%span sinsertion_sort28 = "insertion_sort.rs" 8 8 8 72
   let%span srange29 = "../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter30 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter30 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span sindex31 = "../../../creusot-contracts/src/logic/ops/index.rs" 60 8 60 32
   let%span sindex32 = "../../../creusot-contracts/src/logic/ops/index.rs" 49 8 49 31
   let%span sslice33 = "../../../creusot-contracts/src/std/slice.rs" 257 19 257 35
@@ -39,8 +39,8 @@ module M_insertion_sort__insertion_sort [#"insertion_sort.rs" 21 0 21 40]
   let%span sslice37 = "../../../creusot-contracts/src/std/slice.rs" 29 14 29 42
   let%span sinsertion_sort38 = "insertion_sort.rs" 15 8 15 35
   let%span smodel39 = "../../../creusot-contracts/src/model.rs" 92 8 92 22
-  let%span siter40 = "../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter41 = "../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter40 = "../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter41 = "../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange42 = "../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange43 = "../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange44 = "../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
diff --git a/creusot/tests/should_succeed/iterators/03_std_iterators.coma b/creusot/tests/should_succeed/iterators/03_std_iterators.coma
index 1f3a9b3f1..6e1fc8be1 100644
--- a/creusot/tests/should_succeed/iterators/03_std_iterators.coma
+++ b/creusot/tests/should_succeed/iterators/03_std_iterators.coma
@@ -10,12 +10,12 @@ module M_03_std_iterators__slice_iter [#"03_std_iterators.rs" 6 0 6 42]
   let%span s03_std_iterators8 = "03_std_iterators.rs" 4 11 4 30
   let%span s03_std_iterators9 = "03_std_iterators.rs" 5 10 5 33
   let%span sslice10 = "../../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
-  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span sslice12 = "../../../../creusot-contracts/src/std/slice.rs" 405 12 405 66
-  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span smodel14 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
-  let%span siter15 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter15 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span sslice17 = "../../../../creusot-contracts/src/std/slice.rs" 411 14 411 45
   let%span sslice18 = "../../../../creusot-contracts/src/std/slice.rs" 409 4 409 10
   let%span sslice19 = "../../../../creusot-contracts/src/std/slice.rs" 416 15 416 32
@@ -322,9 +322,9 @@ module M_03_std_iterators__vec_iter [#"03_std_iterators.rs" 17 0 17 41]
   let%span s03_std_iterators7 = "03_std_iterators.rs" 17 19 17 22
   let%span s03_std_iterators8 = "03_std_iterators.rs" 15 11 15 28
   let%span s03_std_iterators9 = "03_std_iterators.rs" 16 10 16 31
-  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span sslice11 = "../../../../creusot-contracts/src/std/slice.rs" 405 12 405 66
-  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span smodel13 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
   let%span svec14 = "../../../../creusot-contracts/src/std/vec.rs" 205 20 205 24
   let%span svec15 = "../../../../creusot-contracts/src/std/vec.rs" 211 20 211 34
@@ -650,18 +650,18 @@ module M_03_std_iterators__all_zero [#"03_std_iterators.rs" 28 0 28 35]
   let%span svec8 = "../../../../creusot-contracts/src/std/vec.rs" 175 26 175 42
   let%span svec9 = "../../../../creusot-contracts/src/std/vec.rs" 176 26 176 48
   let%span sslice10 = "../../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
-  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span sindex12 = "../../../../creusot-contracts/src/logic/ops/index.rs" 93 8 93 33
   let%span sslice13 = "../../../../creusot-contracts/src/std/slice.rs" 459 12 459 66
-  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span svec15 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   let%span smodel16 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
   let%span sindex17 = "../../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
   let%span sslice18 = "../../../../creusot-contracts/src/std/slice.rs" 28 14 28 41
   let%span sslice19 = "../../../../creusot-contracts/src/std/slice.rs" 29 14 29 42
   let%span sslice20 = "../../../../creusot-contracts/src/std/slice.rs" 427 14 427 50
-  let%span siter21 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter22 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter21 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter22 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span sresolve23 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
   let%span sslice24 = "../../../../creusot-contracts/src/std/slice.rs" 465 14 465 45
   let%span sslice25 = "../../../../creusot-contracts/src/std/slice.rs" 463 4 463 10
@@ -992,8 +992,8 @@ end
 module M_03_std_iterators__skip_take [#"03_std_iterators.rs" 35 0 35 48]
   let%span s03_std_iterators0 = "03_std_iterators.rs" 38 20 38 31
   let%span s03_std_iterators1 = "03_std_iterators.rs" 35 30 35 34
-  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
-  let%span siter3 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
+  let%span siter3 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span stake4 = "../../../../creusot-contracts/src/std/iter/take.rs" 17 14 17 39
   let%span stake5 = "../../../../creusot-contracts/src/std/iter/take.rs" 31 14 31 50
   let%span sskip6 = "../../../../creusot-contracts/src/std/iter/skip.rs" 14 14 14 39
@@ -1015,10 +1015,10 @@ module M_03_std_iterators__skip_take [#"03_std_iterators.rs" 35 0 35 48]
   let%span stake22 = "../../../../creusot-contracts/src/std/iter/take.rs" 78 14 78 42
   let%span stake23 = "../../../../creusot-contracts/src/std/iter/take.rs" 24 14 24 68
   let%span stake24 = "../../../../creusot-contracts/src/std/iter/take.rs" 41 8 41 29
-  let%span siter25 = "../../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter26 = "../../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter27 = "../../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter28 = "../../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter25 = "../../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter26 = "../../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter27 = "../../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter28 = "../../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span sresolve29 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
   
   type t_I'0
@@ -1268,14 +1268,14 @@ module M_03_std_iterators__counter [#"03_std_iterators.rs" 41 0 41 27]
   let%span s03_std_iterators6 = "03_std_iterators.rs" 50 23 50 24
   let%span s03_std_iterators7 = "03_std_iterators.rs" 47 23 47 65
   let%span s03_std_iterators8 = "03_std_iterators.rs" 48 22 48 89
-  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 55 21 55 25
-  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 55 27 55 31
-  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 49 15 51 69
-  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 52 15 52 51
-  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 53 15 53 70
-  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 55 4 58 61
-  let%span siter15 = "../../../../creusot-contracts/src/std/iter.rs" 54 14 54 88
-  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 166 26 167 120
+  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 59 21 59 25
+  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 59 27 59 31
+  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 53 15 55 69
+  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 56 15 56 51
+  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 57 15 57 70
+  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 59 4 62 61
+  let%span siter15 = "../../../../creusot-contracts/src/std/iter.rs" 58 14 58 88
+  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 208 26 209 120
   let%span svec17 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   let%span smodel18 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
   let%span sslice19 = "../../../../creusot-contracts/src/std/slice.rs" 411 14 411 45
@@ -1722,11 +1722,11 @@ module M_03_std_iterators__sum_range [#"03_std_iterators.rs" 63 0 63 35]
   let%span s03_std_iterators7 = "03_std_iterators.rs" 67 13 67 14
   let%span s03_std_iterators8 = "03_std_iterators.rs" 61 11 61 18
   let%span s03_std_iterators9 = "03_std_iterators.rs" 62 10 62 21
-  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span srange11 = "../../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
-  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
+  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange15 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange16 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange17 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
@@ -1928,17 +1928,17 @@ module M_03_std_iterators__enumerate_range [#"03_std_iterators.rs" 72 0 72 24]
   let%span s03_std_iterators4 = "03_std_iterators.rs" 73 16 73 93
   let%span s03_std_iterators5 = "03_std_iterators.rs" 74 4 74 7
   let%span s03_std_iterators6 = "03_std_iterators.rs" 74 4 74 7
-  let%span siter7 = "../../../../creusot-contracts/src/std/iter.rs" 150 27 150 99
-  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 151 27 151 115
-  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter7 = "../../../../creusot-contracts/src/std/iter.rs" 192 27 192 99
+  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 193 27 193 115
+  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span sindex10 = "../../../../creusot-contracts/src/logic/ops/index.rs" 93 8 93 33
   let%span senumerate11 = "../../../../creusot-contracts/src/std/iter/enumerate.rs" 72 12 76 113
-  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span srange13 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   let%span srange14 = "../../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
   let%span senumerate15 = "../../../../creusot-contracts/src/std/iter/enumerate.rs" 14 14 14 39
-  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span senumerate18 = "../../../../creusot-contracts/src/std/iter/enumerate.rs" 82 14 82 45
   let%span senumerate19 = "../../../../creusot-contracts/src/std/iter/enumerate.rs" 87 15 87 32
   let%span senumerate20 = "../../../../creusot-contracts/src/std/iter/enumerate.rs" 88 15 88 32
@@ -2253,13 +2253,13 @@ module M_03_std_iterators__my_reverse [#"03_std_iterators.rs" 94 0 94 37]
   let%span s03_std_iterators20 = "03_std_iterators.rs" 93 10 93 44
   let%span sslice21 = "../../../../creusot-contracts/src/std/slice.rs" 245 0 354 1
   let%span smodel22 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
-  let%span siter23 = "../../../../creusot-contracts/src/std/iter.rs" 159 27 159 48
-  let%span siter24 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
-  let%span siter25 = "../../../../creusot-contracts/src/std/iter.rs" 161 26 161 62
+  let%span siter23 = "../../../../creusot-contracts/src/std/iter.rs" 201 27 201 48
+  let%span siter24 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
+  let%span siter25 = "../../../../creusot-contracts/src/std/iter.rs" 203 26 203 62
   let%span s03_std_iterators26 = "03_std_iterators.rs" 89 8 89 60
   let%span s03_std_iterators27 = "03_std_iterators.rs" 82 8 82 58
   let%span szip28 = "../../../../creusot-contracts/src/std/iter/zip.rs" 46 12 49 95
-  let%span siter29 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter29 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span sslice30 = "../../../../creusot-contracts/src/std/slice.rs" 257 19 257 35
   let%span sslice31 = "../../../../creusot-contracts/src/std/slice.rs" 258 19 258 35
   let%span sslice32 = "../../../../creusot-contracts/src/std/slice.rs" 259 18 259 50
@@ -2267,10 +2267,10 @@ module M_03_std_iterators__my_reverse [#"03_std_iterators.rs" 94 0 94 37]
   let%span sslice34 = "../../../../creusot-contracts/src/std/slice.rs" 28 14 28 41
   let%span sslice35 = "../../../../creusot-contracts/src/std/slice.rs" 29 14 29 42
   let%span smodel36 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
-  let%span siter37 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
+  let%span siter37 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
   let%span szip38 = "../../../../creusot-contracts/src/std/iter/zip.rs" 14 14 14 39
   let%span szip39 = "../../../../creusot-contracts/src/std/iter/zip.rs" 21 14 21 39
-  let%span siter40 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter40 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span szip41 = "../../../../creusot-contracts/src/std/iter/zip.rs" 55 14 55 45
   let%span szip42 = "../../../../creusot-contracts/src/std/iter/zip.rs" 60 15 60 32
   let%span szip43 = "../../../../creusot-contracts/src/std/iter/zip.rs" 61 15 61 32
diff --git a/creusot/tests/should_succeed/iterators/08_collect_extend.coma b/creusot/tests/should_succeed/iterators/08_collect_extend.coma
index 50f3f4a7e..b4c00914e 100644
--- a/creusot/tests/should_succeed/iterators/08_collect_extend.coma
+++ b/creusot/tests/should_succeed/iterators/08_collect_extend.coma
@@ -9,19 +9,19 @@ module M_08_collect_extend__extend [#"08_collect_extend.rs" 26 0 26 66]
   let%span s08_collect_extend7 = "08_collect_extend.rs" 26 40 26 43
   let%span s08_collect_extend8 = "08_collect_extend.rs" 26 58 26 62
   let%span s08_collect_extend9 = "08_collect_extend.rs" 23 2 24 82
-  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span smodel11 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
   let%span ssnapshot12 = "../../../../creusot-contracts/src/snapshot.rs" 52 20 52 39
-  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span svec14 = "../../../../creusot-contracts/src/std/vec.rs" 87 26 87 56
   let%span svec15 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span smodel18 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
-  let%span siter19 = "../../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter20 = "../../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter21 = "../../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter22 = "../../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter19 = "../../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter20 = "../../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter21 = "../../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter22 = "../../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span sresolve23 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
   let%span sinvariant24 = "../../../../creusot-contracts/src/invariant.rs" 34 20 34 44
   let%span sseq25 = "../../../../creusot-contracts/src/logic/seq.rs" 633 20 633 95
@@ -332,16 +332,16 @@ module M_08_collect_extend__collect [#"08_collect_extend.rs" 44 0 44 52]
   let%span s08_collect_extend8 = "08_collect_extend.rs" 44 40 44 52
   let%span s08_collect_extend9 = "08_collect_extend.rs" 41 2 42 88
   let%span svec10 = "../../../../creusot-contracts/src/std/vec.rs" 74 26 74 44
-  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span svec12 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span svec14 = "../../../../creusot-contracts/src/std/vec.rs" 87 26 87 56
-  let%span siter15 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
-  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter18 = "../../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter19 = "../../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter20 = "../../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter15 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter16 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
+  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter18 = "../../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter19 = "../../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter20 = "../../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   let%span sresolve21 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
   let%span smodel22 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
   let%span svec23 = "../../../../creusot-contracts/src/std/vec.rs" 65 20 65 41
@@ -621,7 +621,7 @@ module M_08_collect_extend__extend_index [#"08_collect_extend.rs" 55 0 55 51]
   let%span s08_collect_extend0 = "08_collect_extend.rs" 56 16 56 32
   let%span s08_collect_extend1 = "08_collect_extend.rs" 57 16 57 32
   let%span s08_collect_extend2 = "08_collect_extend.rs" 60 20 60 53
-  let%span siter3 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter3 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span s08_collect_extend4 = "08_collect_extend.rs" 26 40 26 43
   let%span s08_collect_extend5 = "08_collect_extend.rs" 26 58 26 62
   let%span s08_collect_extend6 = "08_collect_extend.rs" 23 2 24 82
@@ -821,10 +821,10 @@ module M_08_collect_extend__collect_example [#"08_collect_extend.rs" 65 0 65 56]
   let%span s08_collect_extend5 = "08_collect_extend.rs" 41 2 42 88
   let%span svec6 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   let%span sindex7 = "../../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
-  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 38 14 38 45
-  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 42 15 42 32
-  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 43 15 43 32
-  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 44 14 44 42
+  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 42 14 42 45
+  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 46 15 46 32
+  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 47 15 47 32
+  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 48 14 48 42
   
   type t_I'0
   
diff --git a/creusot/tests/should_succeed/iterators/17_filter.coma b/creusot/tests/should_succeed/iterators/17_filter.coma
index 17b7e10dc..a8a91b04c 100644
--- a/creusot/tests/should_succeed/iterators/17_filter.coma
+++ b/creusot/tests/should_succeed/iterators/17_filter.coma
@@ -750,12 +750,12 @@ end
 module M_17_filter__less_than [#"17_filter.rs" 120 0 120 49]
   let%span s17_filter0 = "17_filter.rs" 118 10 118 70
   let%span s17_filter1 = "17_filter.rs" 119 10 119 79
-  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter2 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span s17_filter3 = "17_filter.rs" 123 22 123 40
-  let%span siter4 = "../../../../creusot-contracts/src/std/iter.rs" 140 27 140 47
-  let%span siter5 = "../../../../creusot-contracts/src/std/iter.rs" 141 27 141 53
-  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 142 27 142 45
-  let%span siter7 = "../../../../creusot-contracts/src/std/iter.rs" 166 26 167 120
+  let%span siter4 = "../../../../creusot-contracts/src/std/iter.rs" 175 27 175 47
+  let%span siter5 = "../../../../creusot-contracts/src/std/iter.rs" 176 27 176 53
+  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 177 27 177 45
+  let%span siter7 = "../../../../creusot-contracts/src/std/iter.rs" 208 26 209 120
   let%span svec8 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   let%span sindex9 = "../../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
   let%span sseq10 = "../../../../creusot-contracts/src/logic/seq.rs" 355 20 355 77
@@ -767,7 +767,7 @@ module M_17_filter__less_than [#"17_filter.rs" 120 0 120 49]
   let%span sfilter16 = "../../../../creusot-contracts/src/std/iter/filter.rs" 15 14 15 39
   let%span sfilter17 = "../../../../creusot-contracts/src/std/iter/filter.rs" 22 14 22 39
   let%span sfilter18 = "../../../../creusot-contracts/src/std/iter/filter.rs" 77 12 79 47
-  let%span sfilter19 = "../../../../creusot-contracts/src/std/iter/filter.rs" 87 12 99 17
+  let%span sfilter19 = "../../../../creusot-contracts/src/std/iter/filter.rs" 87 12 98 143
   let%span svec20 = "../../../../creusot-contracts/src/std/vec.rs" 285 20 285 32
   let%span sresolve21 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
   let%span sops22 = "../../../../creusot-contracts/src/std/ops.rs" 109 15 109 59
@@ -777,10 +777,10 @@ module M_17_filter__less_than [#"17_filter.rs" 120 0 120 49]
   let%span sops26 = "../../../../creusot-contracts/src/std/ops.rs" 121 15 121 26
   let%span sops27 = "../../../../creusot-contracts/src/std/ops.rs" 122 14 122 28
   let%span sops28 = "../../../../creusot-contracts/src/std/ops.rs" 127 14 128 105
-  let%span sfilter29 = "../../../../creusot-contracts/src/std/iter/filter.rs" 105 14 105 45
-  let%span sfilter30 = "../../../../creusot-contracts/src/std/iter/filter.rs" 110 15 110 32
-  let%span sfilter31 = "../../../../creusot-contracts/src/std/iter/filter.rs" 111 15 111 32
-  let%span sfilter32 = "../../../../creusot-contracts/src/std/iter/filter.rs" 112 14 112 42
+  let%span sfilter29 = "../../../../creusot-contracts/src/std/iter/filter.rs" 104 14 104 45
+  let%span sfilter30 = "../../../../creusot-contracts/src/std/iter/filter.rs" 109 15 109 32
+  let%span sfilter31 = "../../../../creusot-contracts/src/std/iter/filter.rs" 110 15 110 32
+  let%span sfilter32 = "../../../../creusot-contracts/src/std/iter/filter.rs" 111 14 111 42
   let%span svec33 = "../../../../creusot-contracts/src/std/vec.rs" 264 12 264 41
   let%span svec34 = "../../../../creusot-contracts/src/std/vec.rs" 257 20 257 57
   let%span svec35 = "../../../../creusot-contracts/src/std/vec.rs" 270 14 270 45
@@ -1026,8 +1026,8 @@ module M_17_filter__less_than [#"17_filter.rs" 120 0 120 49]
     [%#sfilter19] invariant'0 self
      -> unnest'1 (func'0 self) (func'0 succ)
     /\ (exists s : Seq.seq uint32, f : Map.map int int . produces'1 (iter'0 self) s (iter'0 succ)
-    /\ (forall i : int, j : int . 0 <= i /\ i <= j /\ j < Seq.length visited
-     -> 0 <= Map.get f i /\ Map.get f i <= Map.get f j /\ Map.get f j < Seq.length s)
+    /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> 0 <= Map.get f i /\ Map.get f i < Seq.length s)
+    /\ (forall i : int, j : int . 0 <= i /\ i < j /\ j < Seq.length visited  -> Map.get f i < Map.get f j)
     /\ (forall i : int . 0 <= i /\ i < Seq.length visited  -> Seq.get visited i = Seq.get s (Map.get f i))
     /\ (forall i : int . 0 <= i /\ i < Seq.length s
      -> (exists j : int . 0 <= j /\ j < Seq.length visited /\ Map.get f j = i)
diff --git a/creusot/tests/should_succeed/iterators/17_filter/why3session.xml b/creusot/tests/should_succeed/iterators/17_filter/why3session.xml
index 884ef860b..95aec3083 100644
--- a/creusot/tests/should_succeed/iterators/17_filter/why3session.xml
+++ b/creusot/tests/should_succeed/iterators/17_filter/why3session.xml
@@ -184,7 +184,7 @@
   <proof prover="3"><result status="valid" time="0.016191" steps="6576"/></proof>
   </goal>
   <goal name="vc_next&#39;0.20" expl="loop invariant #1" proved="true">
-  <proof prover="3"><result status="valid" time="0.140911" steps="6589"/></proof>
+  <proof prover="3"><result status="valid" time="0.019790" steps="6589"/></proof>
   </goal>
   <goal name="vc_next&#39;0.21" expl="loop invariant #2" proved="true">
   <proof prover="3"><result status="valid" time="0.129962" steps="8004"/></proof>
@@ -227,7 +227,7 @@
        <proof prover="1"><result status="valid" time="0.017256" steps="56"/></proof>
        </goal>
        <goal name="vc_next&#39;0.26.0.1.0.0.4" proved="true">
-       <proof prover="3" timelimit="5"><result status="valid" time="0.216926" steps="14647"/></proof>
+       <proof prover="3" timelimit="5"><result status="valid" time="0.058439" steps="14647"/></proof>
        </goal>
        <goal name="vc_next&#39;0.26.0.1.0.0.5" proved="true">
        <proof prover="3" timelimit="5"><result status="valid" time="0.056568" steps="8027"/></proof>
@@ -267,36 +267,36 @@
  <goal name="vc_less_than&#39;0" proved="true">
  <transf name="split_vc" proved="true" >
   <goal name="vc_less_than&#39;0.0" expl="into_iter &#39;self&#39; type invariant" proved="true">
-  <proof prover="3"><result status="valid" time="0.017634" steps="4540"/></proof>
+  <proof prover="3"><result status="valid" time="0.017634" steps="4609"/></proof>
   </goal>
   <goal name="vc_less_than&#39;0.1" expl="into_iter requires" proved="true">
-  <proof prover="3"><result status="valid" time="0.026326" steps="3117"/></proof>
+  <proof prover="3"><result status="valid" time="0.026326" steps="3182"/></proof>
   </goal>
   <goal name="vc_less_than&#39;0.2" expl="filter &#39;self&#39; type invariant" proved="true">
-  <proof prover="3"><result status="valid" time="0.024106" steps="3151"/></proof>
+  <proof prover="3"><result status="valid" time="0.024106" steps="3216"/></proof>
   </goal>
   <goal name="vc_less_than&#39;0.3" expl="filter &#39;predicate&#39; type invariant" proved="true">
-  <proof prover="3"><result status="valid" time="0.026382" steps="4675"/></proof>
+  <proof prover="3"><result status="valid" time="0.026382" steps="4744"/></proof>
   </goal>
   <goal name="vc_less_than&#39;0.4" expl="filter requires #0" proved="true">
-  <proof prover="3"><result status="valid" time="0.159460" steps="11587"/></proof>
+  <proof prover="3"><result status="valid" time="0.159460" steps="11674"/></proof>
   </goal>
   <goal name="vc_less_than&#39;0.5" expl="filter requires #1" proved="true">
-  <proof prover="3"><result status="valid" time="0.150046" steps="11409"/></proof>
+  <proof prover="3"><result status="valid" time="0.150046" steps="11496"/></proof>
   </goal>
   <goal name="vc_less_than&#39;0.6" expl="filter requires #2" proved="true">
-  <proof prover="3"><result status="valid" time="0.177981" steps="13181"/></proof>
+  <proof prover="3"><result status="valid" time="0.177981" steps="13268"/></proof>
   </goal>
   <goal name="vc_less_than&#39;0.7" expl="collect &#39;self&#39; type invariant" proved="true">
-  <proof prover="3"><result status="valid" time="0.025616" steps="3184"/></proof>
+  <proof prover="3"><result status="valid" time="0.025616" steps="3249"/></proof>
   </goal>
   <goal name="vc_less_than&#39;0.8" expl="less_than ensures #0" proved="true">
-  <proof prover="1"><result status="valid" time="0.085458" steps="193"/></proof>
+  <proof prover="1"><result status="valid" time="0.085458" steps="195"/></proof>
   </goal>
   <goal name="vc_less_than&#39;0.9" expl="less_than ensures #1" proved="true">
   <transf name="use_th" proved="true" arg1="seq.FreeMonoid">
    <goal name="vc_less_than&#39;0.9.0" expl="less_than ensures #1" proved="true">
-   <proof prover="2"><result status="valid" time="0.203558" steps="26917"/></proof>
+   <proof prover="2"><result status="valid" time="0.074162" steps="26926"/></proof>
    </goal>
   </transf>
   </goal>
diff --git a/creusot/tests/should_succeed/iterators/17_filter/why3shapes.gz b/creusot/tests/should_succeed/iterators/17_filter/why3shapes.gz
index 33e837990..918b37f6d 100644
Binary files a/creusot/tests/should_succeed/iterators/17_filter/why3shapes.gz and b/creusot/tests/should_succeed/iterators/17_filter/why3shapes.gz differ
diff --git a/creusot/tests/should_succeed/knapsack_full.coma b/creusot/tests/should_succeed/knapsack_full.coma
index 88a92da69..50f4b8706 100644
--- a/creusot/tests/should_succeed/knapsack_full.coma
+++ b/creusot/tests/should_succeed/knapsack_full.coma
@@ -345,7 +345,7 @@ module M_knapsack_full__knapsack01_dyn [#"knapsack_full.rs" 86 0 86 91]
   let%span svec40 = "../../../creusot-contracts/src/std/vec.rs" 180 22 180 41
   let%span svec41 = "../../../creusot-contracts/src/std/vec.rs" 181 22 181 76
   let%span svec42 = "../../../creusot-contracts/src/std/vec.rs" 83 26 83 48
-  let%span siter43 = "../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter43 = "../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span smodel44 = "../../../creusot-contracts/src/model.rs" 92 8 92 22
   let%span sindex45 = "../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
   let%span svec46 = "../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
@@ -356,13 +356,13 @@ module M_knapsack_full__knapsack01_dyn [#"knapsack_full.rs" 86 0 86 91]
   let%span sknapsack_full51 = "knapsack_full.rs" 60 10 60 11
   let%span sknapsack_full52 = "knapsack_full.rs" 68 4 75 5
   let%span srange53 = "../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter54 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter54 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span svec55 = "../../../creusot-contracts/src/std/vec.rs" 162 27 162 46
   let%span svec56 = "../../../creusot-contracts/src/std/vec.rs" 163 26 163 54
   let%span sops57 = "../../../creusot-contracts/src/std/ops.rs" 219 26 219 53
   let%span sops58 = "../../../creusot-contracts/src/std/ops.rs" 220 26 220 49
   let%span sops59 = "../../../creusot-contracts/src/std/ops.rs" 221 26 221 91
-  let%span srange60 = "../../../creusot-contracts/src/std/iter/range.rs" 66 12 70 76
+  let%span srange60 = "../../../creusot-contracts/src/std/iter/range.rs" 92 12 96 76
   let%span sknapsack_full61 = "knapsack_full.rs" 15 10 15 31
   let%span svec62 = "../../../creusot-contracts/src/std/vec.rs" 152 27 152 46
   let%span svec63 = "../../../creusot-contracts/src/std/vec.rs" 153 26 153 54
@@ -382,8 +382,8 @@ module M_knapsack_full__knapsack01_dyn [#"knapsack_full.rs" 86 0 86 91]
   let%span sknapsack_full77 = "knapsack_full.rs" 36 10 36 19
   let%span sknapsack_full78 = "knapsack_full.rs" 39 4 42 5
   let%span svec79 = "../../../creusot-contracts/src/std/vec.rs" 87 26 87 56
-  let%span siter80 = "../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter81 = "../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter80 = "../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter81 = "../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange82 = "../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange83 = "../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange84 = "../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
@@ -394,15 +394,15 @@ module M_knapsack_full__knapsack01_dyn [#"knapsack_full.rs" 86 0 86 91]
   let%span sslice89 = "../../../creusot-contracts/src/std/slice.rs" 122 20 122 37
   let%span sslice90 = "../../../creusot-contracts/src/std/slice.rs" 129 20 129 37
   let%span sops91 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
-  let%span srange92 = "../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
-  let%span srange93 = "../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
-  let%span srange94 = "../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
-  let%span srange95 = "../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
-  let%span srange96 = "../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
-  let%span srange97 = "../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
-  let%span srange98 = "../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
-  let%span srange99 = "../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
-  let%span srange100 = "../../../creusot-contracts/src/std/iter/range.rs" 58 12 58 57
+  let%span srange92 = "../../../creusot-contracts/src/std/iter/range.rs" 102 14 102 45
+  let%span srange93 = "../../../creusot-contracts/src/std/iter/range.rs" 100 4 100 10
+  let%span srange94 = "../../../creusot-contracts/src/std/iter/range.rs" 107 15 107 32
+  let%span srange95 = "../../../creusot-contracts/src/std/iter/range.rs" 108 15 108 32
+  let%span srange96 = "../../../creusot-contracts/src/std/iter/range.rs" 109 14 109 42
+  let%span srange97 = "../../../creusot-contracts/src/std/iter/range.rs" 105 4 105 10
+  let%span srange98 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange99 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
+  let%span srange100 = "../../../creusot-contracts/src/std/iter/range.rs" 84 12 84 57
   let%span smodel101 = "../../../creusot-contracts/src/model.rs" 110 8 110 22
   let%span sslice102 = "../../../creusot-contracts/src/std/slice.rs" 136 20 136 94
   let%span svec103 = "../../../creusot-contracts/src/std/vec.rs" 65 20 65 41
diff --git a/creusot/tests/should_succeed/rusthorn/inc_max_repeat.coma b/creusot/tests/should_succeed/rusthorn/inc_max_repeat.coma
index c0b381989..ce2a57936 100644
--- a/creusot/tests/should_succeed/rusthorn/inc_max_repeat.coma
+++ b/creusot/tests/should_succeed/rusthorn/inc_max_repeat.coma
@@ -77,12 +77,12 @@ module M_inc_max_repeat__inc_max_repeat [#"inc_max_repeat.rs" 15 0 15 53]
   let%span sinc_max_repeat7 = "inc_max_repeat.rs" 20 15 20 16
   let%span sinc_max_repeat8 = "inc_max_repeat.rs" 22 4 22 37
   let%span sinc_max_repeat9 = "inc_max_repeat.rs" 14 11 14 70
-  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span srange11 = "../../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span sinc_max_repeat13 = "inc_max_repeat.rs" 4 0 5 56
-  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter15 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter15 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange16 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange17 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange18 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
diff --git a/creusot/tests/should_succeed/selection_sort_generic.coma b/creusot/tests/should_succeed/selection_sort_generic.coma
index 3a397dfc7..fa51b6439 100644
--- a/creusot/tests/should_succeed/selection_sort_generic.coma
+++ b/creusot/tests/should_succeed/selection_sort_generic.coma
@@ -20,7 +20,7 @@ module M_selection_sort_generic__selection_sort [#"selection_sort_generic.rs" 30
   let%span sselection_sort_generic18 = "selection_sort_generic.rs" 28 10 28 35
   let%span sselection_sort_generic19 = "selection_sort_generic.rs" 29 10 29 34
   let%span svec20 = "../../../creusot-contracts/src/std/vec.rs" 83 26 83 48
-  let%span siter21 = "../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter21 = "../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span smodel22 = "../../../creusot-contracts/src/model.rs" 101 8 101 28
   let%span sselection_sort_generic23 = "selection_sort_generic.rs" 25 16 25 105
   let%span sselection_sort_generic24 = "selection_sort_generic.rs" 12 8 12 72
@@ -28,7 +28,7 @@ module M_selection_sort_generic__selection_sort [#"selection_sort_generic.rs" 30
   let%span ssnapshot26 = "../../../creusot-contracts/src/snapshot.rs" 52 20 52 39
   let%span sseq27 = "../../../creusot-contracts/src/logic/seq.rs" 316 8 316 41
   let%span srange28 = "../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter29 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter29 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span svec30 = "../../../creusot-contracts/src/std/vec.rs" 162 27 162 46
   let%span svec31 = "../../../creusot-contracts/src/std/vec.rs" 163 26 163 54
   let%span scmp32 = "../../../creusot-contracts/src/std/cmp.rs" 35 26 35 76
@@ -42,8 +42,8 @@ module M_selection_sort_generic__selection_sort [#"selection_sort_generic.rs" 30
   let%span sselection_sort_generic40 = "selection_sort_generic.rs" 19 8 19 35
   let%span svec41 = "../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   let%span smodel42 = "../../../creusot-contracts/src/model.rs" 92 8 92 22
-  let%span siter43 = "../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter44 = "../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter43 = "../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter44 = "../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange45 = "../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange46 = "../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange47 = "../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
diff --git a/creusot/tests/should_succeed/sum.coma b/creusot/tests/should_succeed/sum.coma
index 15558c7c8..68832fb4f 100644
--- a/creusot/tests/should_succeed/sum.coma
+++ b/creusot/tests/should_succeed/sum.coma
@@ -11,22 +11,22 @@ module M_sum__sum_first_n [#"sum.rs" 6 0 6 33]
   let%span sops9 = "../../../creusot-contracts/src/std/ops.rs" 219 26 219 53
   let%span sops10 = "../../../creusot-contracts/src/std/ops.rs" 220 26 220 49
   let%span sops11 = "../../../creusot-contracts/src/std/ops.rs" 221 26 221 91
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
-  let%span srange13 = "../../../creusot-contracts/src/std/iter/range.rs" 66 12 70 76
-  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
+  let%span srange13 = "../../../creusot-contracts/src/std/iter/range.rs" 92 12 96 76
+  let%span siter14 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span snum15 = "../../../creusot-contracts/src/std/num.rs" 21 28 21 33
   let%span sops16 = "../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
-  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
-  let%span srange19 = "../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
-  let%span srange20 = "../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
-  let%span srange21 = "../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
-  let%span srange22 = "../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
-  let%span srange23 = "../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
-  let%span srange24 = "../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
-  let%span srange25 = "../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
-  let%span srange26 = "../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
-  let%span srange27 = "../../../creusot-contracts/src/std/iter/range.rs" 58 12 58 57
+  let%span siter17 = "../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter18 = "../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
+  let%span srange19 = "../../../creusot-contracts/src/std/iter/range.rs" 102 14 102 45
+  let%span srange20 = "../../../creusot-contracts/src/std/iter/range.rs" 100 4 100 10
+  let%span srange21 = "../../../creusot-contracts/src/std/iter/range.rs" 107 15 107 32
+  let%span srange22 = "../../../creusot-contracts/src/std/iter/range.rs" 108 15 108 32
+  let%span srange23 = "../../../creusot-contracts/src/std/iter/range.rs" 109 14 109 42
+  let%span srange24 = "../../../creusot-contracts/src/std/iter/range.rs" 105 4 105 10
+  let%span srange25 = "../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange26 = "../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
+  let%span srange27 = "../../../creusot-contracts/src/std/iter/range.rs" 84 12 84 57
   let%span sresolve28 = "../../../creusot-contracts/src/resolve.rs" 54 20 54 34
   
   use prelude.prelude.UInt32
diff --git a/creusot/tests/should_succeed/sum_of_odds.coma b/creusot/tests/should_succeed/sum_of_odds.coma
index 16c800ba5..2dfa52b16 100644
--- a/creusot/tests/should_succeed/sum_of_odds.coma
+++ b/creusot/tests/should_succeed/sum_of_odds.coma
@@ -59,17 +59,17 @@ module M_sum_of_odds__compute_sum_of_odd [#"sum_of_odds.rs" 36 0 36 36]
   let%span ssum_of_odds9 = "sum_of_odds.rs" 44 21 44 22
   let%span ssum_of_odds10 = "sum_of_odds.rs" 34 11 34 23
   let%span ssum_of_odds11 = "sum_of_odds.rs" 35 10 35 35
-  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter12 = "../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span ssum_of_odds13 = "sum_of_odds.rs" 17 10 17 11
   let%span ssum_of_odds14 = "sum_of_odds.rs" 16 0 16 8
   let%span srange15 = "../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter16 = "../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span ssum_of_odds17 = "sum_of_odds.rs" 27 11 27 17
   let%span ssum_of_odds18 = "sum_of_odds.rs" 28 10 28 33
   let%span ssum_of_odds19 = "sum_of_odds.rs" 29 10 29 11
   let%span ssum_of_odds20 = "sum_of_odds.rs" 31 4 31 65
-  let%span siter21 = "../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter22 = "../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter21 = "../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter22 = "../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange23 = "../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange24 = "../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange25 = "../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
diff --git a/creusot/tests/should_succeed/vector/01.coma b/creusot/tests/should_succeed/vector/01.coma
index 5086234a5..0bf98dd0e 100644
--- a/creusot/tests/should_succeed/vector/01.coma
+++ b/creusot/tests/should_succeed/vector/01.coma
@@ -11,12 +11,12 @@ module M_01__all_zero [#"01.rs" 7 0 7 33]
   let%span s019 = "01.rs" 5 10 5 71
   let%span s0110 = "01.rs" 6 10 6 33
   let%span svec11 = "../../../../creusot-contracts/src/std/vec.rs" 83 26 83 48
-  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span sindex13 = "../../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
   let%span smodel14 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
   let%span ssnapshot15 = "../../../../creusot-contracts/src/snapshot.rs" 52 20 52 39
   let%span srange16 = "../../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span svec18 = "../../../../creusot-contracts/src/std/vec.rs" 152 27 152 46
   let%span svec19 = "../../../../creusot-contracts/src/std/vec.rs" 153 26 153 54
   let%span svec20 = "../../../../creusot-contracts/src/std/vec.rs" 154 26 154 57
@@ -24,8 +24,8 @@ module M_01__all_zero [#"01.rs" 7 0 7 33]
   let%span svec22 = "../../../../creusot-contracts/src/std/vec.rs" 156 26 156 55
   let%span svec23 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   let%span smodel24 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
-  let%span siter25 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter26 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter25 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter26 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange27 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange28 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange29 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
diff --git a/creusot/tests/should_succeed/vector/03_knuth_shuffle.coma b/creusot/tests/should_succeed/vector/03_knuth_shuffle.coma
index 3017bc95e..e02a7f83d 100644
--- a/creusot/tests/should_succeed/vector/03_knuth_shuffle.coma
+++ b/creusot/tests/should_succeed/vector/03_knuth_shuffle.coma
@@ -11,12 +11,12 @@ module M_03_knuth_shuffle__knuth_shuffle [#"03_knuth_shuffle.rs" 13 0 13 39]
   let%span s03_knuth_shuffle9 = "03_knuth_shuffle.rs" 13 24 13 25
   let%span s03_knuth_shuffle10 = "03_knuth_shuffle.rs" 12 10 12 34
   let%span svec11 = "../../../../creusot-contracts/src/std/vec.rs" 83 26 83 48
-  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span smodel13 = "../../../../creusot-contracts/src/model.rs" 110 8 110 22
   let%span ssnapshot14 = "../../../../creusot-contracts/src/snapshot.rs" 52 20 52 39
   let%span sseq15 = "../../../../creusot-contracts/src/logic/seq.rs" 316 8 316 41
   let%span srange16 = "../../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter17 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span s03_knuth_shuffle18 = "03_knuth_shuffle.rs" 6 11 6 19
   let%span s03_knuth_shuffle19 = "03_knuth_shuffle.rs" 7 10 7 40
   let%span svec20 = "../../../../creusot-contracts/src/std/vec.rs" 175 26 175 42
@@ -26,8 +26,8 @@ module M_03_knuth_shuffle__knuth_shuffle [#"03_knuth_shuffle.rs" 13 0 13 39]
   let%span sslice24 = "../../../../creusot-contracts/src/std/slice.rs" 259 18 259 50
   let%span svec25 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   let%span smodel26 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
-  let%span siter27 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter28 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter27 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter28 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange29 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange30 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange31 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
diff --git a/creusot/tests/should_succeed/vector/06_knights_tour.coma b/creusot/tests/should_succeed/vector/06_knights_tour.coma
index 83756e7c9..b2fd5bf00 100644
--- a/creusot/tests/should_succeed/vector/06_knights_tour.coma
+++ b/creusot/tests/should_succeed/vector/06_knights_tour.coma
@@ -98,14 +98,14 @@ module M_06_knights_tour__qyi4580598960913230815__new [#"06_knights_tour.rs" 40
   let%span s06_knights_tour3 = "06_knights_tour.rs" 39 14 39 25
   let%span s06_knights_tour4 = "06_knights_tour.rs" 44 28 44 29
   let%span s06_knights_tour5 = "06_knights_tour.rs" 43 26 43 48
-  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 55 21 55 25
-  let%span siter7 = "../../../../creusot-contracts/src/std/iter.rs" 55 27 55 31
-  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 49 15 51 69
-  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 52 15 52 51
-  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 53 15 53 70
-  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 55 4 58 61
-  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 54 14 54 88
-  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 166 26 167 120
+  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 59 21 59 25
+  let%span siter7 = "../../../../creusot-contracts/src/std/iter.rs" 59 27 59 31
+  let%span siter8 = "../../../../creusot-contracts/src/std/iter.rs" 53 15 55 69
+  let%span siter9 = "../../../../creusot-contracts/src/std/iter.rs" 56 15 56 51
+  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 57 15 57 70
+  let%span siter11 = "../../../../creusot-contracts/src/std/iter.rs" 59 4 62 61
+  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 58 14 58 88
+  let%span siter13 = "../../../../creusot-contracts/src/std/iter.rs" 208 26 209 120
   let%span s06_knights_tour14 = "06_knights_tour.rs" 32 12 34 93
   let%span svec15 = "../../../../creusot-contracts/src/std/vec.rs" 180 22 180 41
   let%span svec16 = "../../../../creusot-contracts/src/std/vec.rs" 181 22 181 76
@@ -729,9 +729,9 @@ module M_06_knights_tour__qyi4580598960913230815__count_degree [#"06_knights_tou
   let%span s06_knights_tour9 = "06_knights_tour.rs" 69 15 69 32
   let%span s06_knights_tour10 = "06_knights_tour.rs" 93 10 93 28
   let%span s06_knights_tour11 = "06_knights_tour.rs" 94 10 94 128
-  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter12 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span svec13 = "../../../../creusot-contracts/src/std/vec.rs" 264 12 264 41
-  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter14 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span s06_knights_tour15 = "06_knights_tour.rs" 12 15 12 52
   let%span s06_knights_tour16 = "06_knights_tour.rs" 13 15 13 52
   let%span s06_knights_tour17 = "06_knights_tour.rs" 14 15 14 46
@@ -1337,11 +1337,11 @@ module M_06_knights_tour__min [#"06_knights_tour.rs" 110 0 110 58]
   let%span s06_knights_tour3 = "06_knights_tour.rs" 114 4 114 7
   let%span s06_knights_tour4 = "06_knights_tour.rs" 114 4 114 7
   let%span s06_knights_tour5 = "06_knights_tour.rs" 108 10 109 60
-  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter6 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span smodel7 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
   let%span sindex8 = "../../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
   let%span sslice9 = "../../../../creusot-contracts/src/std/slice.rs" 405 12 405 66
-  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter10 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span svec11 = "../../../../creusot-contracts/src/std/vec.rs" 205 20 205 24
   let%span svec12 = "../../../../creusot-contracts/src/std/vec.rs" 211 20 211 34
   let%span svec13 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
@@ -1677,11 +1677,11 @@ module M_06_knights_tour__knights_tour [#"06_knights_tour.rs" 135 0 135 69]
   let%span s06_knights_tour28 = "06_knights_tour.rs" 128 11 128 22
   let%span s06_knights_tour29 = "06_knights_tour.rs" 129 10 129 30
   let%span s06_knights_tour30 = "06_knights_tour.rs" 127 0 127 8
-  let%span siter31 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter31 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span s06_knights_tour32 = "06_knights_tour.rs" 63 12 63 75
   let%span s06_knights_tour33 = "06_knights_tour.rs" 32 12 34 93
   let%span srange34 = "../../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
-  let%span siter35 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span siter35 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span svec36 = "../../../../creusot-contracts/src/std/vec.rs" 74 26 74 44
   let%span s06_knights_tour37 = "06_knights_tour.rs" 93 10 93 28
   let%span s06_knights_tour38 = "06_knights_tour.rs" 94 10 94 128
@@ -1700,8 +1700,8 @@ module M_06_knights_tour__knights_tour [#"06_knights_tour.rs" 135 0 135 69]
   let%span s06_knights_tour51 = "06_knights_tour.rs" 69 15 69 32
   let%span svec52 = "../../../../creusot-contracts/src/std/vec.rs" 87 26 87 56
   let%span s06_knights_tour53 = "06_knights_tour.rs" 108 10 109 60
-  let%span siter54 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter55 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter54 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter55 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span srange56 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange57 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   let%span srange58 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
diff --git a/creusot/tests/should_succeed/vector/08_haystack.coma b/creusot/tests/should_succeed/vector/08_haystack.coma
index c7126fd7a..954193c03 100644
--- a/creusot/tests/should_succeed/vector/08_haystack.coma
+++ b/creusot/tests/should_succeed/vector/08_haystack.coma
@@ -19,29 +19,29 @@ module M_08_haystack__search [#"08_haystack.rs" 21 0 21 60]
   let%span sops17 = "../../../../creusot-contracts/src/std/ops.rs" 219 26 219 53
   let%span sops18 = "../../../../creusot-contracts/src/std/ops.rs" 220 26 220 49
   let%span sops19 = "../../../../creusot-contracts/src/std/ops.rs" 221 26 221 91
-  let%span siter20 = "../../../../creusot-contracts/src/std/iter.rs" 97 0 205 1
+  let%span siter20 = "../../../../creusot-contracts/src/std/iter.rs" 132 0 261 1
   let%span smodel21 = "../../../../creusot-contracts/src/model.rs" 92 8 92 22
   let%span s08_haystack22 = "08_haystack.rs" 8 16 11 62
-  let%span srange23 = "../../../../creusot-contracts/src/std/iter/range.rs" 66 12 70 76
-  let%span siter24 = "../../../../creusot-contracts/src/std/iter.rs" 103 26 106 17
+  let%span srange23 = "../../../../creusot-contracts/src/std/iter/range.rs" 92 12 96 76
+  let%span siter24 = "../../../../creusot-contracts/src/std/iter.rs" 138 26 141 17
   let%span srange25 = "../../../../creusot-contracts/src/std/iter/range.rs" 22 12 26 70
   let%span svec26 = "../../../../creusot-contracts/src/std/vec.rs" 162 27 162 46
   let%span svec27 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 54
   let%span snum28 = "../../../../creusot-contracts/src/std/num.rs" 21 28 21 33
   let%span sops29 = "../../../../creusot-contracts/src/std/ops.rs" 205 14 205 86
-  let%span siter30 = "../../../../creusot-contracts/src/std/iter.rs" 82 20 82 24
-  let%span siter31 = "../../../../creusot-contracts/src/std/iter.rs" 88 8 88 19
+  let%span siter30 = "../../../../creusot-contracts/src/std/iter.rs" 86 20 86 24
+  let%span siter31 = "../../../../creusot-contracts/src/std/iter.rs" 92 8 92 19
   let%span svec32 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   let%span sindex33 = "../../../../creusot-contracts/src/logic/ops/index.rs" 27 8 27 31
-  let%span srange34 = "../../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
-  let%span srange35 = "../../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
-  let%span srange36 = "../../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
-  let%span srange37 = "../../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
-  let%span srange38 = "../../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
-  let%span srange39 = "../../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
-  let%span srange40 = "../../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
-  let%span srange41 = "../../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
-  let%span srange42 = "../../../../creusot-contracts/src/std/iter/range.rs" 58 12 58 57
+  let%span srange34 = "../../../../creusot-contracts/src/std/iter/range.rs" 102 14 102 45
+  let%span srange35 = "../../../../creusot-contracts/src/std/iter/range.rs" 100 4 100 10
+  let%span srange36 = "../../../../creusot-contracts/src/std/iter/range.rs" 107 15 107 32
+  let%span srange37 = "../../../../creusot-contracts/src/std/iter/range.rs" 108 15 108 32
+  let%span srange38 = "../../../../creusot-contracts/src/std/iter/range.rs" 109 14 109 42
+  let%span srange39 = "../../../../creusot-contracts/src/std/iter/range.rs" 105 4 105 10
+  let%span srange40 = "../../../../creusot-contracts/src/std/iter/range.rs" 71 10 71 43
+  let%span srange41 = "../../../../creusot-contracts/src/std/iter/range.rs" 73 4 76 5
+  let%span srange42 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 12 84 57
   let%span sresolve43 = "../../../../creusot-contracts/src/resolve.rs" 54 20 54 34
   let%span srange44 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   let%span srange45 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32