Only store a LocalDefId in hir::TraitItem.

compiler/rustc_hir/src/hir.rs

@@ -1907,7 +1907,14 @@ pub struct FnSig<'hir> {
 // so it can fetched later.
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Encodable, Debug)]
 pub struct TraitItemId {
-    pub hir_id: HirId,
+    pub def_id: LocalDefId,
+}
+
+impl TraitItemId {
+    pub fn hir_id(&self) -> HirId {
+        // Items are always HIR owners.
+        HirId::make_owner(self.def_id)
+    }
 }
 
 /// Represents an item declaration within a trait declaration,
@@ -1917,13 +1924,24 @@ pub struct TraitItemId {
 #[derive(Debug)]
 pub struct TraitItem<'hir> {
     pub ident: Ident,
-    pub hir_id: HirId,
+    pub def_id: LocalDefId,
     pub attrs: &'hir [Attribute],
     pub generics: Generics<'hir>,
     pub kind: TraitItemKind<'hir>,
     pub span: Span,
 }
 
+impl TraitItem<'_> {
+    pub fn hir_id(&self) -> HirId {
+        // Items are always HIR owners.
+        HirId::make_owner(self.def_id)
+    }
+
+    pub fn trait_item_id(&self) -> TraitItemId {
+        TraitItemId { def_id: self.def_id }
+    }
+}
+
 /// Represents a trait method's body (or just argument names).
 #[derive(Encodable, Debug, HashStable_Generic)]
 pub enum TraitFn<'hir> {
@@ -2885,9 +2903,10 @@ impl<'hir> Node<'hir> {
 
     pub fn hir_id(&self) -> Option<HirId> {
         match self {
-            Node::Item(Item { def_id, .. }) => Some(HirId::make_owner(*def_id)),
+            Node::Item(Item { def_id, .. }) | Node::TraitItem(TraitItem { def_id, .. }) => {
+                Some(HirId::make_owner(*def_id))
+            }
             Node::ForeignItem(ForeignItem { hir_id, .. })
-            | Node::TraitItem(TraitItem { hir_id, .. })
             | Node::ImplItem(ImplItem { hir_id, .. })
             | Node::Field(StructField { hir_id, .. })
             | Node::AnonConst(AnonConst { hir_id, .. })
@@ -2922,7 +2941,7 @@ mod size_asserts {
     rustc_data_structures::static_assert_size!(super::Ty<'static>, 72);
 
     rustc_data_structures::static_assert_size!(super::Item<'static>, 200);
-    rustc_data_structures::static_assert_size!(super::TraitItem<'static>, 152);
+    rustc_data_structures::static_assert_size!(super::TraitItem<'static>, 144);
     rustc_data_structures::static_assert_size!(super::ImplItem<'static>, 168);
     rustc_data_structures::static_assert_size!(super::ForeignItem<'static>, 160);
 }

compiler/rustc_hir/src/intravisit.rs

@@ -964,12 +964,12 @@ pub fn walk_trait_item<'v, V: Visitor<'v>>(visitor: &mut V, trait_item: &'v Trai
     visitor.visit_generics(&trait_item.generics);
     match trait_item.kind {
         TraitItemKind::Const(ref ty, default) => {
-            visitor.visit_id(trait_item.hir_id);
+            visitor.visit_id(trait_item.hir_id());
             visitor.visit_ty(ty);
             walk_list!(visitor, visit_nested_body, default);
         }
         TraitItemKind::Fn(ref sig, TraitFn::Required(param_names)) => {
-            visitor.visit_id(trait_item.hir_id);
+            visitor.visit_id(trait_item.hir_id());
             visitor.visit_fn_decl(&sig.decl);
             for &param_name in param_names {
                 visitor.visit_ident(param_name);
@@ -981,11 +981,11 @@ pub fn walk_trait_item<'v, V: Visitor<'v>>(visitor: &mut V, trait_item: &'v Trai
                 &sig.decl,
                 body_id,
                 trait_item.span,
-                trait_item.hir_id,
+                trait_item.hir_id(),
             );
         }
         TraitItemKind::Type(bounds, ref default) => {
-            visitor.visit_id(trait_item.hir_id);
+            visitor.visit_id(trait_item.hir_id());
             walk_list!(visitor, visit_param_bound, bounds);
             walk_list!(visitor, visit_ty, default);
         }

compiler/rustc_hir/src/stable_hash_impls.rs

@@ -44,11 +44,11 @@ impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for ItemId {
 }
 
 impl<HirCtx: crate::HashStableContext> ToStableHashKey<HirCtx> for TraitItemId {
-    type KeyType = (DefPathHash, ItemLocalId);
+    type KeyType = DefPathHash;
 
     #[inline]
-    fn to_stable_hash_key(&self, hcx: &HirCtx) -> (DefPathHash, ItemLocalId) {
-        self.hir_id.to_stable_hash_key(hcx)
+    fn to_stable_hash_key(&self, hcx: &HirCtx) -> DefPathHash {
+        hcx.local_def_path_hash(self.def_id)
     }
 }
 
@@ -109,7 +109,7 @@ impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for ImplItemId {
 
 impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for TraitItemId {
     fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
-        hcx.hash_reference_to_item(self.hir_id, hasher)
+        hcx.hash_reference_to_item(self.hir_id(), hasher)
     }
 }
 
@@ -139,7 +139,7 @@ impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for VisibilityKind<'_>
 
 impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for TraitItem<'_> {
     fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
-        let TraitItem { hir_id: _, ident, ref attrs, ref generics, ref kind, span } = *self;
+        let TraitItem { def_id: _, ident, ref attrs, ref generics, ref kind, span } = *self;
 
         hcx.hash_hir_item_like(|hcx| {
             ident.name.hash_stable(hcx, hasher);