rustc_metadata: Filter encoded data more aggressively using DefKind

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2580,7 +2580,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 tcx.all_impls(trait_def_id)
                     .filter(|impl_def_id| {
                         // Consider only accessible traits
-                        tcx.visibility(*impl_def_id).is_accessible_from(self.item_def_id(), tcx)
+                        tcx.visibility(trait_def_id).is_accessible_from(self.item_def_id(), tcx)
                             && tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative
                     })
                     .filter_map(|impl_def_id| tcx.impl_trait_ref(impl_def_id))

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -749,6 +749,10 @@ impl CrateRoot {
 }
 
 impl<'a, 'tcx> CrateMetadataRef<'a> {
+    fn missing(self, descr: &str, id: DefIndex) -> ! {
+        bug!("missing `{descr}` for {:?}", self.local_def_id(id))
+    }
+
     fn raw_proc_macro(self, id: DefIndex) -> &'a ProcMacro {
         // DefIndex's in root.proc_macro_data have a one-to-one correspondence
         // with items in 'raw_proc_macros'.
@@ -782,8 +786,13 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
 
     fn opt_item_ident(self, item_index: DefIndex, sess: &Session) -> Option<Ident> {
         let name = self.opt_item_name(item_index)?;
-        let span =
-            self.root.tables.def_ident_span.get(self, item_index).unwrap().decode((self, sess));
+        let span = self
+            .root
+            .tables
+            .def_ident_span
+            .get(self, item_index)
+            .unwrap_or_else(|| self.missing("def_ident_span", item_index))
+            .decode((self, sess));
         Some(Ident::new(name, span))
     }
 
@@ -812,7 +821,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             .tables
             .def_span
             .get(self, index)
-            .unwrap_or_else(|| panic!("Missing span for {index:?}"))
+            .unwrap_or_else(|| self.missing("def_span", index))
             .decode((self, sess))
     }
 
@@ -924,7 +933,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             .tables
             .visibility
             .get(self, id)
-            .unwrap()
+            .unwrap_or_else(|| self.missing("visibility", id))
             .decode(self)
             .map_id(|index| self.local_def_id(index))
     }
@@ -934,7 +943,12 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
     }
 
     fn get_expn_that_defined(self, id: DefIndex, sess: &Session) -> ExpnId {
-        self.root.tables.expn_that_defined.get(self, id).unwrap().decode((self, sess))
+        self.root
+            .tables
+            .expn_that_defined
+            .get(self, id)
+            .unwrap_or_else(|| self.missing("expn_that_defined", id))
+            .decode((self, sess))
     }
 
     fn get_debugger_visualizers(self) -> Vec<rustc_span::DebuggerVisualizerFile> {

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -811,6 +811,117 @@ fn analyze_attr(attr: &Attribute, state: &mut AnalyzeAttrState) -> bool {
     should_encode
 }
 
+fn should_encode_span(def_kind: DefKind) -> bool {
+    match def_kind {
+        DefKind::Mod
+        | DefKind::Struct
+        | DefKind::Union
+        | DefKind::Enum
+        | DefKind::Variant
+        | DefKind::Trait
+        | DefKind::TyAlias
+        | DefKind::ForeignTy
+        | DefKind::TraitAlias
+        | DefKind::AssocTy
+        | DefKind::TyParam
+        | DefKind::Fn
+        | DefKind::Const
+        | DefKind::Static(_)
+        | DefKind::Ctor(..)
+        | DefKind::AssocFn
+        | DefKind::AssocConst
+        | DefKind::Macro(_)
+        | DefKind::AnonConst
+        | DefKind::InlineConst
+        | DefKind::OpaqueTy
+        | DefKind::Field
+        | DefKind::Impl { .. }
+        | DefKind::Closure
+        | DefKind::Generator => true,
+        DefKind::ConstParam
+        | DefKind::ExternCrate
+        | DefKind::Use
+        | DefKind::ForeignMod
+        | DefKind::ImplTraitPlaceholder
+        | DefKind::LifetimeParam
+        | DefKind::GlobalAsm => false,
+    }
+}
+
+fn should_encode_attrs(def_kind: DefKind) -> bool {
+    match def_kind {
+        DefKind::Mod
+        | DefKind::Struct
+        | DefKind::Union
+        | DefKind::Enum
+        | DefKind::Variant
+        | DefKind::Trait
+        | DefKind::TyAlias
+        | DefKind::ForeignTy
+        | DefKind::TraitAlias
+        | DefKind::AssocTy
+        | DefKind::Fn
+        | DefKind::Const
+        | DefKind::Static(_)
+        | DefKind::AssocFn
+        | DefKind::AssocConst
+        | DefKind::Macro(_)
+        | DefKind::Field
+        | DefKind::Impl { .. } => true,
+        DefKind::TyParam
+        | DefKind::ConstParam
+        | DefKind::Ctor(..)
+        | DefKind::ExternCrate
+        | DefKind::Use
+        | DefKind::ForeignMod
+        | DefKind::AnonConst
+        | DefKind::InlineConst
+        | DefKind::OpaqueTy
+        | DefKind::ImplTraitPlaceholder
+        | DefKind::LifetimeParam
+        | DefKind::GlobalAsm
+        | DefKind::Closure
+        | DefKind::Generator => false,
+    }
+}
+
+fn should_encode_expn_that_defined(def_kind: DefKind) -> bool {
+    match def_kind {
+        DefKind::Mod
+        | DefKind::Struct
+        | DefKind::Union
+        | DefKind::Enum
+        | DefKind::Variant
+        | DefKind::Trait
+        | DefKind::Impl { .. } => true,
+        DefKind::TyAlias
+        | DefKind::ForeignTy
+        | DefKind::TraitAlias
+        | DefKind::AssocTy
+        | DefKind::TyParam
+        | DefKind::Fn
+        | DefKind::Const
+        | DefKind::ConstParam
+        | DefKind::Static(_)
+        | DefKind::Ctor(..)
+        | DefKind::AssocFn
+        | DefKind::AssocConst
+        | DefKind::Macro(_)
+        | DefKind::ExternCrate
+        | DefKind::Use
+        | DefKind::ForeignMod
+        | DefKind::AnonConst
+        | DefKind::InlineConst
+        | DefKind::OpaqueTy
+        | DefKind::ImplTraitPlaceholder
+        | DefKind::Field
+        | DefKind::LifetimeParam
+        | DefKind::GlobalAsm
+        | DefKind::Closure
+        | DefKind::Generator => false,
+    }
+}
+
 fn should_encode_visibility(def_kind: DefKind) -> bool {
     match def_kind {
         DefKind::Mod
@@ -830,18 +941,18 @@ fn should_encode_visibility(def_kind: DefKind) -> bool {
         | DefKind::AssocFn
         | DefKind::AssocConst
         | DefKind::Macro(..)
-        | DefKind::Use
-        | DefKind::ForeignMod
-        | DefKind::OpaqueTy
-        | DefKind::ImplTraitPlaceholder
-        | DefKind::Impl { .. }
         | DefKind::Field => true,
-        DefKind::TyParam
+        DefKind::Use
+        | DefKind::ForeignMod
+        | DefKind::TyParam
         | DefKind::ConstParam
         | DefKind::LifetimeParam
         | DefKind::AnonConst
         | DefKind::InlineConst
+        | DefKind::OpaqueTy
+        | DefKind::ImplTraitPlaceholder
         | DefKind::GlobalAsm
+        | DefKind::Impl { .. }
         | DefKind::Closure
         | DefKind::Generator
         | DefKind::ExternCrate => false,
@@ -1160,11 +1271,17 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             let def_kind = tcx.opt_def_kind(local_id);
             let Some(def_kind) = def_kind else { continue };
             self.tables.opt_def_kind.set_some(def_id.index, def_kind);
-            let def_span = tcx.def_span(local_id);
-            record!(self.tables.def_span[def_id] <- def_span);
-            self.encode_attrs(local_id);
-            record!(self.tables.expn_that_defined[def_id] <- self.tcx.expn_that_defined(def_id));
-            if let Some(ident_span) = tcx.def_ident_span(def_id) {
+            if should_encode_span(def_kind) {
+                let def_span = tcx.def_span(local_id);
+                record!(self.tables.def_span[def_id] <- def_span);
+            }
+            if should_encode_attrs(def_kind) {
+                self.encode_attrs(local_id);
+            }
+            if should_encode_expn_that_defined(def_kind) {
+                record!(self.tables.expn_that_defined[def_id] <- self.tcx.expn_that_defined(def_id));
+            }
+            if should_encode_span(def_kind) && let Some(ident_span) = tcx.def_ident_span(def_id) {
                 record!(self.tables.def_ident_span[def_id] <- ident_span);
             }
             if def_kind.has_codegen_attrs() {

src/librustdoc/clean/types.rs

@@ -687,7 +687,7 @@ impl Item {
                 return None;
             }
             // Variants always inherit visibility
-            VariantItem(..) => return None,
+            VariantItem(..) | ImplItem(..) => return None,
             // Trait items inherit the trait's visibility
             AssocConstItem(..) | TyAssocConstItem(..) | AssocTypeItem(..) | TyAssocTypeItem(..)
             | TyMethodItem(..) | MethodItem(..) => {

tests/ui/associated-types/associated-types-in-ambiguous-context.rs

@@ -1,3 +1,5 @@
+// normalize-stderr-test: "and \d+ other candidates" -> "and N other candidates"
+
 trait Get {
     type Value;
     fn get(&self) -> <Self as Get>::Value;

tests/ui/associated-types/associated-types-in-ambiguous-context.stderr

@@ -1,5 +1,5 @@
 error[E0223]: ambiguous associated type
-  --> $DIR/associated-types-in-ambiguous-context.rs:6:36
+  --> $DIR/associated-types-in-ambiguous-context.rs:8:36
    |
 LL | fn get<T:Get,U:Get>(x: T, y: U) -> Get::Value {}
    |                                    ^^^^^^^^^^
@@ -10,30 +10,37 @@ LL | fn get<T:Get,U:Get>(x: T, y: U) -> <Example as Get>::Value {}
    |                                    ~~~~~~~~~~~~~~~~~~~~~~~
 
 error[E0223]: ambiguous associated type
-  --> $DIR/associated-types-in-ambiguous-context.rs:20:17
+  --> $DIR/associated-types-in-ambiguous-context.rs:22:17
    |
 LL | trait Foo where Foo::Assoc: Bar {
    |                 ^^^^^^^^^^ help: use the fully-qualified path: `<Self as Foo>::Assoc`
 
 error[E0223]: ambiguous associated type
-  --> $DIR/associated-types-in-ambiguous-context.rs:25:10
+  --> $DIR/associated-types-in-ambiguous-context.rs:27:10
    |
 LL | type X = std::ops::Deref::Target;
    |          ^^^^^^^^^^^^^^^^^^^^^^^
    |
-help: if there were a type named `Example` that implemented `Deref`, you could use the fully-qualified path
+help: use the fully-qualified path
    |
-LL | type X = <Example as Deref>::Target;
+LL | type X = <CString as Deref>::Target;
    |          ~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL | type X = <IoSlice<'_> as Deref>::Target;
+   |          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL | type X = <IoSliceMut<'_> as Deref>::Target;
+   |          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL | type X = <OsString as Deref>::Target;
+   |          ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+     and N other candidates
 
 error[E0223]: ambiguous associated type
-  --> $DIR/associated-types-in-ambiguous-context.rs:11:23
+  --> $DIR/associated-types-in-ambiguous-context.rs:13:23
    |
 LL |     fn grab(&self) -> Grab::Value;
    |                       ^^^^^^^^^^^ help: use the fully-qualified path: `<Self as Grab>::Value`
 
 error[E0223]: ambiguous associated type
-  --> $DIR/associated-types-in-ambiguous-context.rs:14:22
+  --> $DIR/associated-types-in-ambiguous-context.rs:16:22
    |
 LL |     fn get(&self) -> Get::Value;
    |                      ^^^^^^^^^^