Start replacing CStore trait methods with hooks.

This also avoids the cyclic definition issues with CrateStore being
defined after TyCtxt, but needing to be used in TyCtxt.

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -378,6 +378,7 @@ provide! { tcx, def_id, other, cdata,
 }
 
 pub(in crate::rmeta) fn provide(providers: &mut Providers) {
+    provide_cstore_hooks(providers);
     // FIXME(#44234) - almost all of these queries have no sub-queries and
     // therefore no actual inputs, they're just reading tables calculated in
     // resolve! Does this work? Unsure! That's what the issue is about
@@ -664,11 +665,14 @@ impl CrateStore for CStore {
     ) -> ExpnId {
         self.get_crate_data(cnum).expn_hash_to_expn_id(sess, index_guess, hash)
     }
+}
 
-    fn import_source_files(&self, sess: &Session, cnum: CrateNum) {
-        let cdata = self.get_crate_data(cnum);
+fn provide_cstore_hooks(providers: &mut Providers) {
+    providers.hooks.import_source_files = |tcx, cnum| {
+        let cstore = CStore::from_tcx(tcx.tcx);
+        let cdata = cstore.get_crate_data(cnum);
         for file_index in 0..cdata.root.source_map.size() {
-            cdata.imported_source_file(file_index as u32, sess);
+            cdata.imported_source_file(file_index as u32, tcx.sess);
         }
-    }
+    };
 }

compiler/rustc_middle/src/hooks/mod.rs

@@ -6,7 +6,7 @@
 use crate::mir;
 use crate::query::TyCtxtAt;
 use crate::ty::{Ty, TyCtxt};
-use rustc_span::def_id::LocalDefId;
+use rustc_span::def_id::{CrateNum, LocalDefId};
 use rustc_span::DUMMY_SP;
 
 macro_rules! declare_hooks {
@@ -16,7 +16,6 @@ macro_rules! declare_hooks {
             $(
             $(#[$attr])*
             #[inline(always)]
-            #[must_use]
             pub fn $name(self, $($arg: $K,)*) -> $V
             {
                 self.at(DUMMY_SP).$name($($arg,)*)
@@ -28,7 +27,6 @@ macro_rules! declare_hooks {
             $(
             $(#[$attr])*
             #[inline(always)]
-            #[must_use]
             #[instrument(level = "debug", skip(self), ret)]
             pub fn $name(self, $($arg: $K,)*) -> $V
             {
@@ -83,4 +81,11 @@ declare_hooks! {
     /// You do not want to call this yourself, instead use the cached version
     /// via `mir_built`
     hook build_mir(key: LocalDefId) -> mir::Body<'tcx>;
+
+
+    /// Imports all `SourceFile`s from the given crate into the current session.
+    /// This normally happens automatically when we decode a `Span` from
+    /// that crate's metadata - however, the incr comp cache needs
+    /// to trigger this manually when decoding a foreign `Span`
+    hook import_source_files(key: CrateNum) -> ();
 }

compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -492,9 +492,7 @@ impl<'a, 'tcx> CacheDecoder<'a, 'tcx> {
                 // expansion, so we use `import_source_files` to ensure that the foreign
                 // source files are actually imported before we call `source_file_by_stable_id`.
                 if source_file_cnum != LOCAL_CRATE {
-                    self.tcx
-                        .cstore_untracked()
-                        .import_source_files(self.tcx.sess, source_file_cnum);
+                    self.tcx.import_source_files(source_file_cnum);
                 }
 
                 source_map

compiler/rustc_session/src/cstore.rs

@@ -230,12 +230,6 @@ pub trait CrateStore: std::fmt::Debug {
         index_guess: u32,
         hash: ExpnHash,
     ) -> ExpnId;
-
-    /// Imports all `SourceFile`s from the given crate into the current session.
-    /// This normally happens automatically when we decode a `Span` from
-    /// that crate's metadata - however, the incr comp cache needs
-    /// to trigger this manually when decoding a foreign `Span`
-    fn import_source_files(&self, sess: &Session, cnum: CrateNum);
 }
 
 pub type CrateStoreDyn = dyn CrateStore + sync::DynSync + sync::DynSend;