Fix and test 'Hylo.DynamicBuffer'

Library/Hylo/Core/Linear.hylo

@@ -0,0 +1,2 @@
+/// A type whose instances are movable and deinitializable.
+public trait Linear: Deinitializable, Movable {}

Library/Hylo/DynamicBuffer.hylo

@@ -1,5 +1,9 @@
 /// A buffer of elements stored in a contiguous region of memory, whose size is determined at
 /// instance creation.
+///
+/// - Warning: The deinitializer of `DynamicBuffer` does not deinitialize the elements that may
+///   be stored in its payload. You must ensure that they are properly deinitialized before
+///   `deinit` is called.
 public type DynamicBuffer<Header: Deinitializable, Element>: Deinitializable {
 
   /// The description of payloads in `DynamicBuffer`s.
@@ -36,15 +40,27 @@ public type DynamicBuffer<Header: Deinitializable, Element>: Deinitializable {
     &storage = .allocate_bytes(
       count: Self.payload_offset() + capacity * MemoryLayout<Element>.stride(),
       aligned_at: MemoryLayout<BufferHeader>.alignment())
+
+    let p = PointerToMutable<BufferHeader>(type_punning: storage)
+    p.unsafe_initialize_pointee(fun (_ h: set BufferHeader) -> Void {
+      &h.0 = capacity.copy()
+      init_header(&h.1)
+    })
   }
 
   /// Deinitializes `self`.
+  ///
+  /// - Requires: No element is stored in `self`.
   public fun deinit() sink {
     storage.deallocate()
   }
 
   /// The number of elements that can be stored in `self`.
   public fun capacity() -> Int {
+    if storage == PointerToMutable.null() {
+      return 0
+    }
+
     let p = PointerToMutable<BufferHeader>(type_punning: storage)
     return p.unsafe[].0.copy()
   }

Sources/IR/Analysis/Module+Depolymorphize.swift

@@ -6,8 +6,7 @@ extension Module {
 
   /// Generates the non-parametric resilient API of `self`, reading definitions from `ir`.
   public mutating func depolymorphize(in ir: IR.Program) {
-    let work = functions.keys
-    for k in work {
+    for k in functions.keys {
       let f = functions[k]!
 
       // Ignore declarations without definition.

Sources/IR/Emitter.swift

@@ -1260,8 +1260,13 @@ struct Emitter {
       let l = emit(infixOperand: lhs, passed: ParameterType(calleeType.inputs[0].type)!.access)
 
       // The callee must be a reference to member function.
-      guard case .member(let d, _, _) = program[callee.expr].referredDecl else { unreachable() }
-      let f = Operand.constant(FunctionReference(to: FunctionDecl.ID(d)!, in: &module))
+      guard case .member(let d, let a, _) = program[callee.expr].referredDecl else {
+        unreachable()
+      }
+
+      let o = FunctionReference(
+        to: FunctionDecl.ID(d)!, in: &module, specializedBy: a, in: insertionScope!)
+      let f = Operand.constant(o)
 
       // Emit the call.
       let site = ast.site(of: e)

Tests/LibraryTests/TestCases/DynamicBufferTests.hylo

@@ -0,0 +1,18 @@
+//- compileAndRun expecting: success
+
+fun test_init_empty() {
+  var d = DynamicBuffer<Int, Int>()
+  precondition(d.capacity() == 0)
+}
+
+fun test_init_with_capacity() {
+  var d = DynamicBuffer<Int, Int>(
+    capacity: 5,
+    initializing_header_with: fun(_ h: set Int) -> Void { &h = 0 })
+  precondition(d.capacity() == 5)
+}
+
+public fun main() {
+  test_init_empty()
+  test_init_with_capacity()  
+}