Feed and only optionally encode item attrs if theyre present

Author: compiler-errors

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1141,19 +1141,19 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             .tables
             .attributes
             .get(self, id)
-            .unwrap_or_else(|| {
+            .or_else(|| {
                 // Structure and variant constructors don't have any attributes encoded for them,
                 // but we assume that someone passing a constructor ID actually wants to look at
                 // the attributes on the corresponding struct or variant.
                 let def_key = self.def_key(id);
-                assert_eq!(def_key.disambiguated_data.data, DefPathData::Ctor);
-                let parent_id = def_key.parent.expect("no parent for a constructor");
-                self.root
-                    .tables
-                    .attributes
-                    .get(self, parent_id)
-                    .expect("no encoded attributes for a structure or variant")
+                if def_key.disambiguated_data.data == DefPathData::Ctor {
+                    let parent_id = def_key.parent.expect("no parent for a constructor");
+                    self.root.tables.attributes.get(self, parent_id)
+                } else {
+                    None
+                }
             })
+            .unwrap_or_else(|| LazyArray::default())
             .decode((self, sess))
     }
 

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1284,13 +1284,12 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             is_exported: tcx.effective_visibilities(()).is_exported(def_id),
             is_doc_hidden: false,
         };
-        let attr_iter = tcx
-            .opt_local_def_id_to_hir_id(def_id)
-            .map_or(Default::default(), |hir_id| tcx.hir().attrs(hir_id))
-            .iter()
-            .filter(|attr| analyze_attr(attr, &mut state));
 
-        record_array!(self.tables.attributes[def_id.to_def_id()] <- attr_iter);
+        let item_attrs = tcx.item_attrs(def_id);
+        if !item_attrs.is_empty() {
+            let attr_iter = item_attrs.iter().filter(|attr| analyze_attr(attr, &mut state));
+            record_array!(self.tables.attributes[def_id.to_def_id()] <- attr_iter);
+        }
 
         let mut attr_flags = AttrFlags::empty();
         if state.is_doc_hidden {

compiler/rustc_middle/src/query/mod.rs

@@ -1214,6 +1214,7 @@ rustc_queries! {
     query item_attrs(def_id: DefId) -> &'tcx [ast::Attribute] {
         desc { |tcx| "collecting attributes of `{}`", tcx.def_path_str(def_id) }
         separate_provide_extern
+        feedable
     }
 
     query codegen_fn_attrs(def_id: DefId) -> &'tcx CodegenFnAttrs {

compiler/rustc_ty_utils/src/assoc.rs

@@ -256,6 +256,8 @@ fn associated_type_for_impl_trait_in_trait(
     let local_def_id = trait_assoc_ty.def_id();
     let def_id = local_def_id.to_def_id();
 
+    trait_assoc_ty.item_attrs(&[]);
+
     trait_assoc_ty.opt_def_kind(Some(DefKind::AssocTy));
 
     // There's no HIR associated with this new synthesized `def_id`, so feed
@@ -351,6 +353,8 @@ fn associated_type_for_impl_trait_in_impl(
     let local_def_id = impl_assoc_ty.def_id();
     let def_id = local_def_id.to_def_id();
 
+    impl_assoc_ty.item_attrs(&[]);
+
     impl_assoc_ty.opt_def_kind(Some(DefKind::AssocTy));
 
     // There's no HIR associated with this new synthesized `def_id`, so feed