Introduce a hir_owner_parent query.

Author: cjgillot

compiler/rustc_middle/src/hir/map/mod.rs

@@ -285,8 +285,7 @@ impl<'hir> Map<'hir> {
 
     pub fn find_parent_node(&self, id: HirId) -> Option<HirId> {
         if id.local_id == ItemLocalId::from_u32(0) {
-            let index = self.tcx.index_hir(LOCAL_CRATE);
-            index.parenting.get(&id.owner).copied()
+            Some(self.tcx.hir_owner_parent(id.owner))
         } else {
             let owner = self.tcx.hir_owner_nodes(id.owner)?;
             let node = owner.nodes[id.local_id].as_ref()?;

compiler/rustc_middle/src/hir/mod.rs

@@ -129,6 +129,10 @@ pub fn provide(providers: &mut Providers) {
     providers.hir_module_items = |tcx, id| &tcx.untracked_crate.modules[&id];
     providers.hir_owner = |tcx, id| tcx.index_hir(LOCAL_CRATE).map[id].signature;
     providers.hir_owner_nodes = |tcx, id| tcx.index_hir(LOCAL_CRATE).map[id].with_bodies.as_deref();
+    providers.hir_owner_parent = |tcx, id| {
+        let index = tcx.index_hir(LOCAL_CRATE);
+        index.parenting.get(&id).copied().unwrap_or(CRATE_HIR_ID)
+    };
     providers.hir_attrs = |tcx, id| AttributeMap { map: &tcx.untracked_crate.attrs, prefix: id };
     providers.def_span = |tcx, def_id| tcx.hir().span_if_local(def_id).unwrap_or(DUMMY_SP);
     providers.fn_arg_names = |tcx, id| {

compiler/rustc_middle/src/query/mod.rs

@@ -52,6 +52,15 @@ rustc_queries! {
         desc { |tcx| "HIR owner of `{}`", tcx.def_path_str(key.to_def_id()) }
     }
 
+    /// Gives access to the HIR node's parent for the HIR owner `key`.
+    ///
+    /// This can be conveniently accessed by methods on `tcx.hir()`.
+    /// Avoid calling this query directly.
+    query hir_owner_parent(key: LocalDefId) -> hir::HirId {
+        eval_always
+        desc { |tcx| "HIR parent of `{}`", tcx.def_path_str(key.to_def_id()) }
+    }
+
     /// Gives access to the HIR nodes and bodies inside the HIR owner `key`.
     ///
     /// This can be conveniently accessed by methods on `tcx.hir()`.