Make def names and HIR names consistent.

compiler/rustc_hir/src/definitions.rs

@@ -147,6 +147,11 @@ impl DefKey {
         // DefPathHashes in this DefPathTable.
         DefPathHash::new(parent.stable_crate_id(), local_hash)
     }
+
+    #[inline]
+    pub fn get_opt_name(&self) -> Option<Symbol> {
+        self.disambiguated_data.data.get_opt_name()
+    }
 }
 
 /// A pair of `DefPathData` and an integer disambiguator. The integer is

compiler/rustc_middle/src/hir/map/mod.rs

@@ -1,5 +1,5 @@
 use crate::hir::{ModuleItems, Owner};
-use crate::ty::TyCtxt;
+use crate::ty::{DefIdTree, TyCtxt};
 use rustc_ast as ast;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
@@ -545,23 +545,21 @@ impl<'hir> Map<'hir> {
         });
     }
 
-    pub fn ty_param_owner(self, id: HirId) -> LocalDefId {
-        match self.get(id) {
-            Node::Item(&Item { kind: ItemKind::Trait(..) | ItemKind::TraitAlias(..), .. }) => {
-                id.expect_owner()
-            }
-            Node::GenericParam(_) => self.get_parent_item(id),
-            _ => bug!("ty_param_owner: {} not a type parameter", self.node_to_string(id)),
+    pub fn ty_param_owner(self, def_id: LocalDefId) -> LocalDefId {
+        let def_kind = self.tcx.def_kind(def_id);
+        match def_kind {
+            DefKind::Trait | DefKind::TraitAlias => def_id,
+            DefKind::TyParam | DefKind::ConstParam => self.tcx.local_parent(def_id).unwrap(),
+            _ => bug!("ty_param_owner: {:?} is a {:?} not a type parameter", def_id, def_kind),
         }
     }
 
-    pub fn ty_param_name(self, id: HirId) -> Symbol {
-        match self.get(id) {
-            Node::Item(&Item { kind: ItemKind::Trait(..) | ItemKind::TraitAlias(..), .. }) => {
-                kw::SelfUpper
-            }
-            Node::GenericParam(param) => param.name.ident().name,
-            _ => bug!("ty_param_name: {} not a type parameter", self.node_to_string(id)),
+    pub fn ty_param_name(self, def_id: LocalDefId) -> Symbol {
+        let def_kind = self.tcx.def_kind(def_id);
+        match def_kind {
+            DefKind::Trait | DefKind::TraitAlias => kw::SelfUpper,
+            DefKind::TyParam | DefKind::ConstParam => self.tcx.item_name(def_id.to_def_id()),
+            _ => bug!("ty_param_name: {:?} is a {:?} not a type parameter", def_id, def_kind),
         }
     }
 

compiler/rustc_middle/src/query/mod.rs

@@ -517,10 +517,7 @@ rustc_queries! {
     /// To avoid cycles within the predicates of a single item we compute
     /// per-type-parameter predicates for resolving `T::AssocTy`.
     query type_param_predicates(key: (DefId, LocalDefId, rustc_span::symbol::Ident)) -> ty::GenericPredicates<'tcx> {
-        desc { |tcx| "computing the bounds for type parameter `{}`", {
-            let id = tcx.hir().local_def_id_to_hir_id(key.1);
-            tcx.hir().ty_param_name(id)
-        }}
+        desc { |tcx| "computing the bounds for type parameter `{}`", tcx.hir().ty_param_name(key.1) }
     }
 
     query trait_def(key: DefId) -> ty::TraitDef {

compiler/rustc_middle/src/ty/mod.rs

@@ -1986,27 +1986,25 @@ impl<'tcx> TyCtxt<'tcx> {
             .filter(|item| item.kind == AssocKind::Fn && item.defaultness.has_value())
     }
 
-    fn item_name_from_hir(self, def_id: DefId) -> Option<Ident> {
-        self.hir().get_if_local(def_id).and_then(|node| node.ident())
-    }
-
-    fn item_name_from_def_id(self, def_id: DefId) -> Option<Symbol> {
+    fn opt_item_name(self, def_id: DefId) -> Option<Symbol> {
         if def_id.index == CRATE_DEF_INDEX {
             Some(self.crate_name(def_id.krate))
         } else {
             let def_key = self.def_key(def_id);
             match def_key.disambiguated_data.data {
                 // The name of a constructor is that of its parent.
-                rustc_hir::definitions::DefPathData::Ctor => self.item_name_from_def_id(DefId {
-                    krate: def_id.krate,
-                    index: def_key.parent.unwrap(),
-                }),
-                _ => def_key.disambiguated_data.data.get_opt_name(),
+                rustc_hir::definitions::DefPathData::Ctor => self
+                    .opt_item_name(DefId { krate: def_id.krate, index: def_key.parent.unwrap() }),
+                // The name of opaque types only exists in HIR.
+                rustc_hir::definitions::DefPathData::ImplTrait
+                    if let Some(def_id) = def_id.as_local() =>
+                    self.hir().opt_name(self.hir().local_def_id_to_hir_id(def_id)),
+                _ => def_key.get_opt_name(),
             }
         }
     }
 
-    /// Look up the name of an item across crates. This does not look at HIR.
+    /// Look up the name of a definition across crates. This does not look at HIR.
     ///
     /// When possible, this function should be used for cross-crate lookups over
     /// [`opt_item_name`] to avoid invalidating the incremental cache. If you
@@ -2018,18 +2016,21 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn item_name(self, id: DefId) -> Symbol {
         // Look at cross-crate items first to avoid invalidating the incremental cache
         // unless we have to.
-        self.item_name_from_def_id(id).unwrap_or_else(|| {
+        self.opt_item_name(id).unwrap_or_else(|| {
             bug!("item_name: no name for {:?}", self.def_path(id));
         })
     }
 
-    /// Look up the name and span of an item or [`Node`].
+    /// Look up the name and span of a definition.
     ///
     /// See [`item_name`][Self::item_name] for more information.
-    pub fn opt_item_name(self, def_id: DefId) -> Option<Ident> {
-        // Look at the HIR first so the span will be correct if this is a local item.
-        self.item_name_from_hir(def_id)
-            .or_else(|| self.item_name_from_def_id(def_id).map(Ident::with_dummy_span))
+    pub fn opt_item_ident(self, def_id: DefId) -> Option<Ident> {
+        let def = self.opt_item_name(def_id)?;
+        let span = def_id
+            .as_local()
+            .and_then(|id| self.def_ident_span(id))
+            .unwrap_or(rustc_span::DUMMY_SP);
+        Some(Ident::new(def, span))
     }
 
     pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> {

compiler/rustc_monomorphize/src/polymorphize.rs

@@ -201,7 +201,7 @@ fn emit_unused_generic_params_error<'tcx>(
         return;
     }
 
-    let fn_span = match tcx.opt_item_name(def_id) {
+    let fn_span = match tcx.opt_item_ident(def_id) {
         Some(ident) => ident.span,
         _ => tcx.def_span(def_id),
     };

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -2064,7 +2064,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             ObligationCauseCode::BindingObligation(item_def_id, span) => {
                 let item_name = tcx.def_path_str(item_def_id);
                 let mut multispan = MultiSpan::from(span);
-                if let Some(ident) = tcx.opt_item_name(item_def_id) {
+                if let Some(ident) = tcx.opt_item_ident(item_def_id) {
                     let sm = tcx.sess.source_map();
                     let same_line =
                         match (sm.lookup_line(ident.span.hi()), sm.lookup_line(span.lo())) {
@@ -2267,7 +2267,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 if !is_upvar_tys_infer_tuple {
                     let msg = format!("required because it appears within the type `{}`", ty);
                     match ty.kind() {
-                        ty::Adt(def, _) => match self.tcx.opt_item_name(def.did()) {
+                        ty::Adt(def, _) => match self.tcx.opt_item_ident(def.did()) {
                             Some(ident) => err.span_note(ident.span, &msg),
                             None => err.note(&msg),
                         },
@@ -2475,7 +2475,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 );
                 let sp = self
                     .tcx
-                    .opt_item_name(trait_item_def_id)
+                    .opt_item_ident(trait_item_def_id)
                     .map(|i| i.span)
                     .unwrap_or_else(|| self.tcx.def_span(trait_item_def_id));
                 let mut assoc_span: MultiSpan = sp.into();
@@ -2486,7 +2486,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 if let Some(ident) = self
                     .tcx
                     .opt_associated_item(trait_item_def_id)
-                    .and_then(|i| self.tcx.opt_item_name(i.container.id()))
+                    .and_then(|i| self.tcx.opt_item_ident(i.container.id()))
                 {
                     assoc_span.push_span_label(ident.span, "in this trait");
                 }
@@ -2511,7 +2511,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 if let Some(ident) = self
                     .tcx
                     .opt_associated_item(trait_item_def_id)
-                    .and_then(|i| self.tcx.opt_item_name(i.container.id()))
+                    .and_then(|i| self.tcx.opt_item_ident(i.container.id()))
                 {
                     assoc_span.push_span_label(ident.span, "in this trait");
                 }

compiler/rustc_typeck/src/astconv/generics.rs

@@ -82,8 +82,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 }
                 Res::Def(DefKind::TyParam, src_def_id) => {
                     if let Some(param_local_id) = param.def_id.as_local() {
-                        let param_hir_id = tcx.hir().local_def_id_to_hir_id(param_local_id);
-                        let param_name = tcx.hir().ty_param_name(param_hir_id);
+                        let param_name = tcx.hir().ty_param_name(param_local_id);
                         let param_type = tcx.infer_ctxt().enter(|infcx| {
                             infcx.resolve_numeric_literals_with_default(tcx.type_of(param.def_id))
                         });

compiler/rustc_typeck/src/astconv/mod.rs

@@ -1620,8 +1620,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
         debug!("find_bound_for_assoc_item: predicates={:#?}", predicates);
 
-        let param_hir_id = tcx.hir().local_def_id_to_hir_id(ty_param_def_id);
-        let param_name = tcx.hir().ty_param_name(param_hir_id);
+        let param_name = tcx.hir().ty_param_name(ty_param_def_id);
         self.one_bound_for_assoc_type(
             || {
                 traits::transitive_bounds_that_define_assoc_type(
@@ -2265,12 +2264,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 assert_eq!(opt_self_ty, None);
                 self.prohibit_generics(path.segments);
 
-                let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
-                let item_id = tcx.hir().get_parent_node(hir_id);
-                let item_def_id = tcx.hir().local_def_id(item_id);
+                let def_id = def_id.expect_local();
+                let item_def_id = tcx.hir().ty_param_owner(def_id);
                 let generics = tcx.generics_of(item_def_id);
-                let index = generics.param_def_id_to_index[&def_id];
-                tcx.mk_ty_param(index, tcx.hir().name(hir_id))
+                let index = generics.param_def_id_to_index[&def_id.to_def_id()];
+                tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id))
             }
             Res::SelfTy { trait_: Some(_), alias_to: None } => {
                 // `Self` in trait or type alias.

compiler/rustc_typeck/src/check/expr.rs

@@ -2195,7 +2195,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             None => return,
         };
         let param_span = self.tcx.hir().span(param_hir_id);
-        let param_name = self.tcx.hir().ty_param_name(param_hir_id);
+        let param_name = self.tcx.hir().ty_param_name(param_def_id.expect_local());
 
         err.span_label(param_span, &format!("type parameter '{}' declared here", param_name));
     }

compiler/rustc_typeck/src/check/fn_ctxt/mod.rs

@@ -184,8 +184,7 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
         _: Ident,
     ) -> ty::GenericPredicates<'tcx> {
         let tcx = self.tcx;
-        let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
-        let item_def_id = tcx.hir().ty_param_owner(hir_id);
+        let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
         let generics = tcx.generics_of(item_def_id);
         let index = generics.param_def_id_to_index[&def_id];
         ty::GenericPredicates {

compiler/rustc_typeck/src/collect.rs

@@ -558,10 +558,10 @@ fn type_param_predicates(
     // `where T: Foo`.
 
     let param_id = tcx.hir().local_def_id_to_hir_id(def_id);
-    let param_owner = tcx.hir().ty_param_owner(param_id);
+    let param_owner = tcx.hir().ty_param_owner(def_id);
     let generics = tcx.generics_of(param_owner);
     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
-    let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
+    let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id));
 
     // Don't look for bounds where the type parameter isn't in scope.
     let parent = if item_def_id == param_owner.to_def_id() {

src/test/ui/const-generics/occurs-check/unused-substs-1.stderr

@@ -8,6 +8,9 @@ LL |     let _ = A;
 note: required by a bound in `A`
   --> $DIR/unused-substs-1.rs:9:11
    |
+LL | struct A<const N: usize>
+   |        - required by a bound in this
+LL | where
 LL |     A<N>: Bar<N>;
    |           ^^^^^^ required by this bound in `A`