Auto merge of #92159 - petrochenkov:decoditer, r=cjgillot

rustc_metadata: Switch crate data iteration from a callback to iterator

The iteration looks more conventional this way, and some allocations are avoided.

1 files changed, 3 insertions, 5 deletions

diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index b46a92e2c1b..06b72d537c2 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -372,7 +372,7 @@ pub fn provide(providers: &mut Providers) {
             tcx.arena
                 .alloc_slice(&CStore::from_tcx(tcx).crate_dependencies_in_postorder(LOCAL_CRATE))
         },
-        crates: |tcx, ()| tcx.arena.alloc_slice(&CStore::from_tcx(tcx).crates_untracked()),
+        crates: |tcx, ()| tcx.arena.alloc_from_iter(CStore::from_tcx(tcx).crates_untracked()),
 
         ..*providers
     };
@@ -449,10 +449,8 @@ impl CStore {
         self.get_crate_data(def.krate).def_kind(def.index)
     }
 
-    pub fn crates_untracked(&self) -> Vec<CrateNum> {
-        let mut result = vec![];
-        self.iter_crate_data(|cnum, _| result.push(cnum));
-        result
+    pub fn crates_untracked(&self) -> impl Iterator<Item = CrateNum> + '_ {
+        self.iter_crate_data().map(|(cnum, _)| cnum)
     }
 
     pub fn item_generics_num_lifetimes(&self, def_id: DefId, sess: &Session) -> usize {