Auto merge of #86857 - fee1-dead:add-attr, r=oli-obk

Add #[default_method_body_is_const]

`@rustbot` label F-const_trait_impl

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -952,6 +952,10 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
         self.get_impl_data(id).defaultness
     }
 
+    fn get_impl_constness(&self, id: DefIndex) -> hir::Constness {
+        self.get_impl_data(id).constness
+    }
+
     fn get_coerce_unsized_info(&self, id: DefIndex) -> Option<ty::adjustment::CoerceUnsizedInfo> {
         self.get_impl_data(id).coerce_unsized_info
     }

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

@@ -168,6 +168,7 @@ provide! { <'tcx> tcx, def_id, other, cdata,
     is_no_builtins => { cdata.root.no_builtins }
     symbol_mangling_version => { cdata.root.symbol_mangling_version }
     impl_defaultness => { cdata.get_impl_defaultness(def_id.index) }
+    impl_constness => { cdata.get_impl_constness(def_id.index) }
     reachable_non_generics => {
         let reachable_non_generics = tcx
             .exported_symbols(cdata.cnum)

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1412,7 +1412,7 @@ impl EncodeContext<'a, 'tcx> {
                     adt_def.repr,
                 )
             }
-            hir::ItemKind::Impl(hir::Impl { defaultness, .. }) => {
+            hir::ItemKind::Impl(hir::Impl { defaultness, constness, .. }) => {
                 let trait_ref = self.tcx.impl_trait_ref(def_id);
                 let polarity = self.tcx.impl_polarity(def_id);
                 let parent = if let Some(trait_ref) = trait_ref {
@@ -1437,8 +1437,13 @@ impl EncodeContext<'a, 'tcx> {
                     }
                 });
 
-                let data =
-                    ImplData { polarity, defaultness, parent_impl: parent, coerce_unsized_info };
+                let data = ImplData {
+                    polarity,
+                    defaultness,
+                    constness,
+                    parent_impl: parent,
+                    coerce_unsized_info,
+                };
 
                 EntryKind::Impl(self.lazy(data))
             }

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -390,6 +390,7 @@ struct TraitData {
 #[derive(TyEncodable, TyDecodable)]
 struct ImplData {
     polarity: ty::ImplPolarity,
+    constness: hir::Constness,
     defaultness: hir::Defaultness,
     parent_impl: Option<DefId>,