Auto merge of #123126 - oli-obk:feed_crate_num, r=davidtwco

Enable `CrateNum` query feeding via `TyCtxt`

Instead of having a magic function that violates some `TyCtxtFeed` invariants, add a `create_def` equivalent for `CrateNum`s.

Note that this still isn't tracked by the query system (unlike `create_def`), and that feeding most `CrateNum` queries for crates other than the local one will likely cause performance regressions.

These things should be attempted on their own separately, but this PR should stand on its own

compiler/rustc_middle/src/ty/context.rs

@@ -565,13 +565,6 @@ impl<'tcx> TyCtxt<'tcx> {
         TyCtxtFeed { tcx: self, key: () }
     }
 
-    /// Can only be fed before queries are run, and is thus exempt from any
-    /// incremental issues. Do not use except for the initial query feeding.
-    pub fn feed_local_crate(self) -> TyCtxtFeed<'tcx, CrateNum> {
-        self.dep_graph.assert_ignored();
-        TyCtxtFeed { tcx: self, key: LOCAL_CRATE }
-    }
-
     /// Only used in the resolver to register the `CRATE_DEF_ID` `DefId` and feed
     /// some queries for it. It will panic if used twice.
     pub fn create_local_crate_def_id(self, span: Span) -> TyCtxtFeed<'tcx, LocalDefId> {
@@ -1151,7 +1144,12 @@ impl<'tcx> TyCtxt<'tcx> {
         if stable_crate_id == self.stable_crate_id(LOCAL_CRATE) {
             LOCAL_CRATE
         } else {
-            self.cstore_untracked().stable_crate_id_to_crate_num(stable_crate_id)
+            *self
+                .untracked()
+                .stable_crate_ids
+                .read()
+                .get(&stable_crate_id)
+                .unwrap_or_else(|| bug!("uninterned StableCrateId: {stable_crate_id:?}"))
         }
     }
 
@@ -1267,6 +1265,19 @@ impl<'tcx> TyCtxt<'tcx> {
         feed
     }
 
+    pub fn create_crate_num(
+        self,
+        stable_crate_id: StableCrateId,
+    ) -> Result<TyCtxtFeed<'tcx, CrateNum>, CrateNum> {
+        if let Some(&existing) = self.untracked().stable_crate_ids.read().get(&stable_crate_id) {
+            return Err(existing);
+        }
+
+        let num = CrateNum::new(self.untracked().stable_crate_ids.read().len());
+        self.untracked().stable_crate_ids.write().insert(stable_crate_id, num);
+        Ok(TyCtxtFeed { key: num, tcx: self })
+    }
+
     pub fn iter_local_def_id(self) -> impl Iterator<Item = LocalDefId> + 'tcx {
         // Create a dependency to the red node to be sure we re-execute this when the amount of
         // definitions change.