Auto merge of #110542 - petrochenkov:qcstore4, r=cjgillot

resolve: Remove `module_children_untracked`

One of the expensive spans in `ModChild` was removed in #109772, so let's try again.

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

@@ -516,14 +516,6 @@ impl CStore {
         self.get_crate_data(def.krate).get_ctor(def.index)
     }
 
-    pub fn module_children_untracked<'a>(
-        &'a self,
-        def_id: DefId,
-        sess: &'a Session,
-    ) -> impl Iterator<Item = ModChild> + 'a {
-        self.get_crate_data(def_id.krate).get_module_children(def_id.index, sess)
-    }
-
     pub fn load_macro_untracked(&self, id: DefId, sess: &Session) -> LoadedMacro {
         let _prof_timer = sess.prof.generic_activity("metadata_load_macro");
 

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -197,10 +197,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
     }
 
     pub(crate) fn build_reduced_graph_external(&mut self, module: Module<'a>) {
-        // Query `module_children` is not used because hashing spans in its result is expensive.
-        let children =
-            Vec::from_iter(self.cstore().module_children_untracked(module.def_id(), self.tcx.sess));
-        for child in children {
+        for child in self.tcx.module_children(module.def_id()) {
             let parent_scope = ParentScope::module(module, self);
             BuildReducedGraphVisitor { r: self, parent_scope }
                 .build_reduced_graph_for_external_crate_res(child);
@@ -929,9 +926,9 @@ impl<'a, 'b, 'tcx> BuildReducedGraphVisitor<'a, 'b, 'tcx> {
     }
 
     /// Builds the reduced graph for a single item in an external crate.
-    fn build_reduced_graph_for_external_crate_res(&mut self, child: ModChild) {
+    fn build_reduced_graph_for_external_crate_res(&mut self, child: &ModChild) {
         let parent = self.parent_scope.module;
-        let ModChild { ident, res, vis, reexport_chain } = child;
+        let ModChild { ident, res, vis, ref reexport_chain } = *child;
         let span = self.r.def_span(
             reexport_chain
                 .first()