Simplify the creation of synthetic HIR.

Author: cjgillot

compiler/rustc_hir/src/hir.rs

@@ -1595,6 +1595,20 @@ impl<'tcx> OwnerNodes<'tcx> {
         // Indexing must ensure it is an OwnerNode.
         self.nodes[ItemLocalId::ZERO].node.as_owner().unwrap()
     }
+
+    /// Return an instance of `OwnerNodes` suitable for definitions that have no corresponding AST.
+    pub fn synthetic() -> OwnerNodes<'tcx> {
+        OwnerNodes {
+            // There is no reason to bother computing a hash for a synthetic body.
+            // Just use a constant value.
+            opt_hash_including_bodies: Some(Fingerprint::ZERO),
+            nodes: IndexVec::from_elem_n(
+                ParentedNode { parent: ItemLocalId::INVALID, node: OwnerNode::Synthetic.into() },
+                1,
+            ),
+            bodies: SortedMap::new(),
+        }
+    }
 }
 
 impl fmt::Debug for OwnerNodes<'_> {

compiler/rustc_middle/src/ty/context.rs

@@ -623,23 +623,8 @@ impl<'tcx> TyCtxtFeed<'tcx, LocalDefId> {
     // Fills in all the important parts needed by HIR queries
     pub fn feed_hir(&self) {
         self.local_def_id_to_hir_id(HirId::make_owner(self.def_id()));
-
-        let node = hir::OwnerNode::Synthetic;
-        let bodies = Default::default();
-        let attrs = hir::AttributeMap::EMPTY;
-
-        let rustc_middle::hir::Hashes { opt_hash_including_bodies, .. } =
-            self.tcx.hash_owner_nodes(node, &bodies, &attrs.map, attrs.define_opaque);
-        let node = node.into();
-        self.opt_hir_owner_nodes(Some(self.tcx.arena.alloc(hir::OwnerNodes {
-            opt_hash_including_bodies,
-            nodes: IndexVec::from_elem_n(
-                hir::ParentedNode { parent: hir::ItemLocalId::INVALID, node },
-                1,
-            ),
-            bodies,
-        })));
-        self.feed_owner_id().hir_attr_map(attrs);
+        self.opt_hir_owner_nodes(Some(self.tcx.arena.alloc(hir::OwnerNodes::synthetic())));
+        self.feed_owner_id().hir_attr_map(hir::AttributeMap::EMPTY);
     }
 }