Use identifiers in diagnostics more often

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -2362,7 +2362,7 @@ fn try_report_async_mismatch<'tcx>(
             // the right span is a bit difficult.
             return Err(tcx.sess.dcx().emit_err(MethodShouldReturnFuture {
                 span: tcx.def_span(impl_m.def_id),
-                method_name: trait_m.name,
+                method_name: tcx.item_ident(impl_m.def_id),
                 trait_item_span: tcx.hir().span_if_local(trait_m.def_id),
             }));
         }

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -197,7 +197,7 @@ fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId) {
 
 fn report_forbidden_specialization(tcx: TyCtxt<'_>, impl_item: DefId, parent_impl: DefId) {
     let span = tcx.def_span(impl_item);
-    let ident = tcx.item_name(impl_item);
+    let ident = tcx.item_ident(impl_item);
 
     let err = match tcx.span_of_impl(parent_impl) {
         Ok(sp) => errors::ImplNotMarkedDefault::Ok { span, ident, ok_label: sp },
@@ -297,7 +297,7 @@ fn default_body_is_unstable(
     reason: Option<Symbol>,
     issue: Option<NonZero<u32>>,
 ) {
-    let missing_item_name = tcx.associated_item(item_did).name;
+    let missing_item_name = tcx.item_ident(item_did);
     let (mut some_note, mut none_note, mut reason_str) = (false, false, String::new());
     match reason {
         Some(r) => {

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -292,7 +292,7 @@ fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<()
 
                         res = Err(tcx.dcx().emit_err(errors::DispatchFromDynZST {
                             span,
-                            name: field.name,
+                            name: field.ident(tcx),
                             ty: ty_a,
                         }));
 

compiler/rustc_hir_analysis/src/coherence/orphan.rs

@@ -465,8 +465,8 @@ fn emit_orphan_check_error<'tcx>(
         traits::OrphanCheckErr::UncoveredTyParams(UncoveredTyParams { uncovered, local_ty }) => {
             let mut reported = None;
             for param_def_id in uncovered {
-                let span = tcx.def_ident_span(param_def_id).unwrap();
+                let name = tcx.item_ident(param_def_id);
-                let name = tcx.item_name(param_def_id);
+                let span = name.span;
 
                 reported.get_or_insert(match local_ty {
                     Some(local_type) => tcx.dcx().emit_err(errors::TyParamFirstLocal {
@@ -492,7 +492,7 @@ fn lint_uncovered_ty_params<'tcx>(
 
     for param_def_id in uncovered {
         let span = tcx.def_ident_span(param_def_id).unwrap();
-        let name = tcx.item_name(param_def_id);
+        let name = tcx.item_ident(param_def_id);
 
         match local_ty {
             Some(local_type) => tcx.emit_node_span_lint(

compiler/rustc_hir_analysis/src/collect.rs

@@ -928,7 +928,7 @@ fn lower_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId) {
                 tcx.dcx().emit_err(errors::EnumDiscriminantOverflowed {
                     span,
                     discr: prev_discr.unwrap().to_string(),
-                    item_name: tcx.item_name(variant.def_id),
+                    item_name: tcx.item_ident(variant.def_id),
                     wrapped_discr: wrapped_discr.to_string(),
                 });
                 None
@@ -990,11 +990,10 @@ impl<'tcx> FieldUniquenessCheckContext<'tcx> {
     }
 
     /// Check if a given field `ident` declared at `field_decl` has been declared elsewhere before.
-    fn check_field_decl(&mut self, ident: Ident, field_decl: FieldDeclSpan) {
+    fn check_field_decl(&mut self, field_name: Ident, field_decl: FieldDeclSpan) {
         use FieldDeclSpan::*;
-        let field_name = ident.name;
+        let field_name = field_name.normalize_to_macros_2_0();
-        let ident = ident.normalize_to_macros_2_0();
+        match (field_decl, self.seen_fields.get(&field_name).copied()) {
-        match (field_decl, self.seen_fields.get(&ident).copied()) {
             (NotNested(span), Some(NotNested(prev_span))) => {
                 self.tcx.dcx().emit_err(errors::FieldAlreadyDeclared::NotNested {
                     field_name,
@@ -1035,7 +1034,7 @@ impl<'tcx> FieldUniquenessCheckContext<'tcx> {
                 });
             }
             (field_decl, None) => {
-                self.seen_fields.insert(ident, field_decl);
+                self.seen_fields.insert(field_name, field_decl);
             }
         }
     }

compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs

@@ -55,7 +55,7 @@ pub(super) fn find_opaque_ty_constraints_for_impl_trait_in_assoc_type(
     } else {
         let reported = tcx.dcx().emit_err(UnconstrainedOpaqueType {
             span: tcx.def_span(def_id),
-            name: tcx.item_name(parent_def_id.to_def_id()),
+            name: tcx.item_ident(parent_def_id.to_def_id()),
             what: "impl",
         });
         Ty::new_error(tcx, reported)
@@ -136,7 +136,7 @@ pub(super) fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: Local
         }
         let reported = tcx.dcx().emit_err(UnconstrainedOpaqueType {
             span: tcx.def_span(def_id),
-            name: tcx.item_name(parent_def_id.to_def_id()),
+            name: tcx.item_ident(parent_def_id.to_def_id()),
             what: match tcx.hir_node(scope) {
                 _ if scope == hir::CRATE_HIR_ID => "module",
                 Node::Item(hir::Item { kind: hir::ItemKind::Mod(_), .. }) => "module",

compiler/rustc_hir_analysis/src/errors.rs

@@ -217,7 +217,7 @@ pub(crate) struct DropImplOnWrongItem {
 pub(crate) enum FieldAlreadyDeclared {
     #[diag(hir_analysis_field_already_declared, code = E0124)]
     NotNested {
-        field_name: Symbol,
+        field_name: Ident,
         #[primary_span]
         #[label]
         span: Span,
@@ -226,7 +226,7 @@ pub(crate) enum FieldAlreadyDeclared {
     },
     #[diag(hir_analysis_field_already_declared_current_nested)]
     CurrentNested {
-        field_name: Symbol,
+        field_name: Ident,
         #[primary_span]
         #[label]
         span: Span,
@@ -239,7 +239,7 @@ pub(crate) enum FieldAlreadyDeclared {
     },
     #[diag(hir_analysis_field_already_declared_previous_nested)]
     PreviousNested {
-        field_name: Symbol,
+        field_name: Ident,
         #[primary_span]
         #[label]
         span: Span,
@@ -252,7 +252,7 @@ pub(crate) enum FieldAlreadyDeclared {
     },
     #[diag(hir_analysis_field_already_declared_both_nested)]
     BothNested {
-        field_name: Symbol,
+        field_name: Ident,
         #[primary_span]
         #[label]
         span: Span,
@@ -418,7 +418,7 @@ pub(crate) struct ValueOfAssociatedStructAlreadySpecified {
 pub(crate) struct UnconstrainedOpaqueType {
     #[primary_span]
     pub span: Span,
-    pub name: Symbol,
+    pub name: Ident,
     pub what: &'static str,
 }
 
@@ -802,7 +802,7 @@ pub(crate) struct EnumDiscriminantOverflowed {
     #[label]
     pub span: Span,
     pub discr: String,
-    pub item_name: Symbol,
+    pub item_name: Ident,
     pub wrapped_discr: String,
 }
 
@@ -893,7 +893,7 @@ pub(crate) enum ImplNotMarkedDefault {
         span: Span,
         #[label(hir_analysis_ok_label)]
         ok_label: Span,
-        ident: Symbol,
+        ident: Ident,
     },
     #[diag(hir_analysis_impl_not_marked_default_err, code = E0520)]
     #[note]
@@ -901,7 +901,7 @@ pub(crate) enum ImplNotMarkedDefault {
         #[primary_span]
         span: Span,
         cname: Symbol,
-        ident: Symbol,
+        ident: Ident,
     },
 }
 
@@ -977,7 +977,7 @@ pub(crate) struct MissingTraitItemUnstable {
     pub some_note: bool,
     #[note(hir_analysis_none_note)]
     pub none_note: bool,
-    pub missing_item_name: Symbol,
+    pub missing_item_name: Ident,
     pub feature: Symbol,
     pub reason: String,
 }
@@ -1249,7 +1249,7 @@ pub(crate) struct InherentNominal {
 pub(crate) struct DispatchFromDynZST<'a> {
     #[primary_span]
     pub span: Span,
-    pub name: Symbol,
+    pub name: Ident,
     pub ty: Ty<'a>,
 }
 
@@ -1389,7 +1389,7 @@ pub(crate) struct TyParamFirstLocal<'tcx> {
     pub span: Span,
     #[note(hir_analysis_case_note)]
     pub note: (),
-    pub param: Symbol,
+    pub param: Ident,
     pub local_type: Ty<'tcx>,
 }
 
@@ -1401,7 +1401,7 @@ pub(crate) struct TyParamFirstLocalLint<'tcx> {
     pub span: Span,
     #[note(hir_analysis_case_note)]
     pub note: (),
-    pub param: Symbol,
+    pub param: Ident,
     pub local_type: Ty<'tcx>,
 }
 
@@ -1414,7 +1414,7 @@ pub(crate) struct TyParamSome {
     pub span: Span,
     #[note(hir_analysis_only_note)]
     pub note: (),
-    pub param: Symbol,
+    pub param: Ident,
 }
 
 #[derive(LintDiagnostic)]
@@ -1425,7 +1425,7 @@ pub(crate) struct TyParamSomeLint {
     pub span: Span,
     #[note(hir_analysis_only_note)]
     pub note: (),
-    pub param: Symbol,
+    pub param: Ident,
 }
 
 #[derive(Diagnostic)]
@@ -1533,7 +1533,7 @@ pub(crate) struct UnsupportedDelegation<'a> {
 pub(crate) struct MethodShouldReturnFuture {
     #[primary_span]
     pub span: Span,
-    pub method_name: Symbol,
+    pub method_name: Ident,
     #[note]
     pub trait_item_span: Option<Span>,
 }
@@ -1585,7 +1585,7 @@ pub(crate) struct UnconstrainedGenericParameter {
     #[primary_span]
     #[label]
     pub span: Span,
-    pub param_name: Symbol,
+    pub param_name: Ident,
     pub param_def_kind: &'static str,
     #[note(hir_analysis_const_param_note)]
     pub const_param_note: bool,

compiler/rustc_hir_analysis/src/impl_wf_check.rs

@@ -152,7 +152,7 @@ pub(crate) fn enforce_impl_lifetime_params_are_constrained(
                 {
                     let mut diag = tcx.dcx().create_err(UnconstrainedGenericParameter {
                         span: tcx.def_span(param.def_id),
-                        param_name: param.name,
+                        param_name: tcx.item_ident(param.def_id),
                         param_def_kind: tcx.def_descr(param.def_id),
                         const_param_note: false,
                         const_param_note2: false,
@@ -223,7 +223,7 @@ pub(crate) fn enforce_impl_non_lifetime_params_are_constrained(
             let const_param_note = matches!(param.kind, ty::GenericParamDefKind::Const { .. });
             let mut diag = tcx.dcx().create_err(UnconstrainedGenericParameter {
                 span: tcx.def_span(param.def_id),
-                param_name: param.name,
+                param_name: tcx.item_ident(param.def_id),
                 param_def_kind: tcx.def_descr(param.def_id),
                 const_param_note,
                 const_param_note2: const_param_note,

compiler/rustc_lint/src/dangling.rs

@@ -141,7 +141,7 @@ fn lint_expr(cx: &LateContext<'_>, expr: &Expr<'_>) {
             expr.hir_id,
             method.ident.span,
             DanglingPointersFromTemporaries {
-                callee: method.ident.name,
+                callee: method.ident,
                 ty,
                 ptr_span: method.ident.span,
                 temporary_span: receiver.span,

compiler/rustc_lint/src/lints.rs

@@ -1132,7 +1132,7 @@ pub(crate) struct IgnoredUnlessCrateSpecified<'a> {
 #[help(lint_help_visit)]
 // FIXME: put #[primary_span] on `ptr_span` once it does not cause conflicts
 pub(crate) struct DanglingPointersFromTemporaries<'tcx> {
-    pub callee: Symbol,
+    pub callee: Ident,
     pub ty: Ty<'tcx>,
     #[label(lint_label_ptr)]
     pub ptr_span: Span,
@@ -1333,7 +1333,7 @@ pub(crate) enum NonUpperCaseGlobalSub {
 #[diag(lint_noop_method_call)]
 #[note]
 pub(crate) struct NoopMethodCallDiag<'a> {
-    pub method: Symbol,
+    pub method: Ident,
     pub orig_ty: Ty<'a>,
     pub trait_: Symbol,
     #[suggestion(code = "", applicability = "machine-applicable")]

compiler/rustc_lint/src/noop_method_call.rs

@@ -129,7 +129,7 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
                 _ => None,
             };
             cx.emit_span_lint(NOOP_METHOD_CALL, span, NoopMethodCallDiag {
-                method: call.ident.name,
+                method: call.ident,
                 orig_ty,
                 trait_,
                 label: span,

compiler/rustc_middle/src/ty/mod.rs

@@ -1596,6 +1596,15 @@ impl<'tcx> TyCtxt<'tcx> {
         Some(Ident::new(def, span))
     }
 
+    /// Look up the name and span of a definition.
+    ///
+    /// See [`item_name`][Self::item_name] for more information.
+    pub fn item_ident(self, def_id: DefId) -> Ident {
+        self.opt_item_ident(def_id).unwrap_or_else(|| {
+            bug!("item_ident: no name for {:?}", self.def_path(def_id));
+        })
+    }
+
     pub fn opt_associated_item(self, def_id: DefId) -> Option<AssocItem> {
         if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
             Some(self.associated_item(def_id))

compiler/rustc_mir_build/src/errors.rs

@@ -7,7 +7,7 @@ use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::{self, Ty};
 use rustc_pattern_analysis::errors::Uncovered;
 use rustc_pattern_analysis::rustc::RustcPatCtxt;
-use rustc_span::{Span, Symbol};
+use rustc_span::{Ident, Span, Symbol};
 
 use crate::fluent_generated as fluent;
 
@@ -753,7 +753,7 @@ pub(crate) struct BindingsWithVariantName {
     #[suggestion(code = "{ty_path}::{name}", applicability = "machine-applicable")]
     pub(crate) suggestion: Option<Span>,
     pub(crate) ty_path: String,
-    pub(crate) name: Symbol,
+    pub(crate) name: Ident,
 }
 
 #[derive(LintDiagnostic)]
@@ -797,7 +797,7 @@ pub(crate) struct BorrowOfMovedValue {
     pub(crate) binding_span: Span,
     #[label(mir_build_value_borrowed_label)]
     pub(crate) conflicts_ref: Vec<Span>,
-    pub(crate) name: Symbol,
+    pub(crate) name: Ident,
     pub(crate) ty: String,
     #[suggestion(code = "ref ", applicability = "machine-applicable")]
     pub(crate) suggest_borrowing: Option<Span>,

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -25,7 +25,7 @@ use rustc_session::lint::builtin::{
 };
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::hygiene::DesugaringKind;
-use rustc_span::{Span, sym};
+use rustc_span::{Ident, Span, sym};
 use rustc_trait_selection::infer::InferCtxtExt;
 use tracing::instrument;
 
@@ -800,7 +800,7 @@ fn check_borrow_conflicts_in_at_patterns<'tcx>(cx: &MatchVisitor<'_, 'tcx>, pat:
                 sess.dcx().emit_err(BorrowOfMovedValue {
                     binding_span: pat.span,
                     conflicts_ref,
-                    name,
+                    name: Ident::new(name, pat.span),
                     ty,
                     suggest_borrowing: Some(pat.span.shrink_to_lo()),
                     has_path: path.is_some(),
@@ -908,7 +908,7 @@ fn check_for_bindings_named_same_as_variants(
                     None
                 },
                 ty_path,
-                name,
+                name: Ident::new(name, pat.span),
             },
         )
     }

compiler/rustc_parse/src/errors.rs

@@ -3233,7 +3233,7 @@ pub(crate) struct MalformedCfgAttr {
 pub(crate) struct UnknownBuiltinConstruct {
     #[primary_span]
     pub span: Span,
-    pub name: Symbol,
+    pub name: Ident,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_parse/src/parser/expr.rs

@@ -1958,7 +1958,7 @@ impl<'a> Parser<'a> {
         } else {
             let err = self.dcx().create_err(errors::UnknownBuiltinConstruct {
                 span: lo.to(ident.span),
-                name: ident.name,
+                name: ident,
             });
             return Err(err);
         };

compiler/rustc_resolve/src/diagnostics.rs

@@ -677,7 +677,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 }
                 if could_be_path {
                     let import_suggestions = self.lookup_import_candidates(
-                        Ident::with_dummy_span(name),
+                        name,
                         Namespace::ValueNS,
                         &parent_scope,
                         &|res: Res| {

compiler/rustc_resolve/src/errors.rs

@@ -59,7 +59,7 @@ pub(crate) struct NameAlreadyUsedInParameterList {
     pub(crate) span: Span,
     #[label(resolve_first_use_of_name)]
     pub(crate) first_use_span: Span,
-    pub(crate) name: Symbol,
+    pub(crate) name: Ident,
 }
 
 #[derive(Diagnostic)]
@@ -142,7 +142,7 @@ pub(crate) struct VariableBoundWithDifferentMode {
     pub(crate) span: Span,
     #[label(resolve_first_binding_span)]
     pub(crate) first_binding_span: Span,
-    pub(crate) variable_name: Symbol,
+    pub(crate) variable_name: Ident,
 }
 
 #[derive(Diagnostic)]
@@ -151,7 +151,7 @@ pub(crate) struct IdentifierBoundMoreThanOnceInParameterList {
     #[primary_span]
     #[label]
     pub(crate) span: Span,
-    pub(crate) identifier: Symbol,
+    pub(crate) identifier: Ident,
 }
 
 #[derive(Diagnostic)]
@@ -160,7 +160,7 @@ pub(crate) struct IdentifierBoundMoreThanOnceInSamePattern {
     #[primary_span]
     #[label]
     pub(crate) span: Span,
-    pub(crate) identifier: Symbol,
+    pub(crate) identifier: Ident,
 }
 
 #[derive(Diagnostic)]
@@ -478,7 +478,7 @@ pub(crate) struct TraitImplDuplicate {
     pub(crate) old_span: Span,
     #[label(resolve_trait_item_span)]
     pub(crate) trait_item_span: Span,
-    pub(crate) name: Symbol,
+    pub(crate) name: Ident,
 }
 
 #[derive(Diagnostic)]
@@ -976,7 +976,7 @@ pub(crate) struct AttemptToDefineBuiltinMacroTwice {
 pub(crate) struct VariableIsNotBoundInAllPatterns {
     #[primary_span]
     pub(crate) multispan: MultiSpan,
-    pub(crate) name: Symbol,
+    pub(crate) name: Ident,
 }
 
 #[derive(Subdiagnostic, Debug, Clone)]
@@ -984,7 +984,7 @@ pub(crate) struct VariableIsNotBoundInAllPatterns {
 pub(crate) struct PatternDoesntBindName {
     #[primary_span]
     pub(crate) span: Span,
-    pub(crate) name: Symbol,
+    pub(crate) name: Ident,
 }
 
 #[derive(Subdiagnostic, Debug, Clone)]
@@ -1260,7 +1260,7 @@ pub(crate) struct TraitImplMismatch {
     #[primary_span]
     #[label]
     pub(crate) span: Span,
-    pub(crate) name: Symbol,
+    pub(crate) name: Ident,
     pub(crate) kind: &'static str,
     pub(crate) trait_path: String,
     #[label(resolve_trait_impl_mismatch_label_item)]

compiler/rustc_resolve/src/late.rs

@@ -2835,7 +2835,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 match seen_bindings.entry(ident) {
                     Entry::Occupied(entry) => {
                         let span = *entry.get();
-                        let err = ResolutionError::NameAlreadyUsedInParameterList(ident.name, span);
+                        let err = ResolutionError::NameAlreadyUsedInParameterList(ident, span);
                         self.report_error(param.ident.span, err);
                         let rib = match param.kind {
                             GenericParamKind::Lifetime => {
@@ -3422,7 +3422,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         match seen_trait_items.entry(id_in_trait) {
             Entry::Occupied(entry) => {
                 self.report_error(span, ResolutionError::TraitImplDuplicate {
-                    name: ident.name,
+                    name: ident,
                     old_span: *entry.get(),
                     trait_item_span: binding.span,
                 });
@@ -3457,7 +3457,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         };
         let trait_path = path_names_to_string(path);
         self.report_error(span, ResolutionError::TraitImplMismatch {
-            name: ident.name,
+            name: ident,
             kind,
             code,
             trait_path,
@@ -3640,9 +3640,8 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 .filter(|(_, pat)| pat.id != pat_outer.id)
                 .flat_map(|(map, _)| map);
 
-            for (key, binding_inner) in inners {
+            for (&name, binding_inner) in inners {
-                let name = key.name;
+                match map_outer.get(&name) {
-                match map_outer.get(key) {
                     None => {
                         // The inner binding is missing in the outer.
                         let binding_error =
@@ -3880,7 +3879,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 // `Variant(a, a)`:
                 _ => IdentifierBoundMoreThanOnceInSamePattern,
             };
-            self.report_error(ident.span, error(ident.name));
+            self.report_error(ident.span, error(ident));
         }
 
         // Record as bound if it's valid:

compiler/rustc_resolve/src/lib.rs

@@ -214,7 +214,7 @@ enum Used {
 
 #[derive(Debug)]
 struct BindingError {
-    name: Symbol,
+    name: Ident,
     origin: BTreeSet<Span>,
     target: BTreeSet<Span>,
     could_be_path: bool,
@@ -226,7 +226,7 @@ enum ResolutionError<'ra> {
     GenericParamsFromOuterItem(Res, HasGenericParams, DefKind),
     /// Error E0403: the name is already used for a type or const parameter in this generic
     /// parameter list.
-    NameAlreadyUsedInParameterList(Symbol, Span),
+    NameAlreadyUsedInParameterList(Ident, Span),
     /// Error E0407: method is not a member of trait.
     MethodNotMemberOfTrait(Ident, String, Option<Symbol>),
     /// Error E0437: type is not a member of trait.
@@ -236,11 +236,11 @@ enum ResolutionError<'ra> {
     /// Error E0408: variable `{}` is not bound in all patterns.
     VariableNotBoundInPattern(BindingError, ParentScope<'ra>),
     /// Error E0409: variable `{}` is bound in inconsistent ways within the same match arm.
-    VariableBoundWithDifferentMode(Symbol, Span),
+    VariableBoundWithDifferentMode(Ident, Span),
     /// Error E0415: identifier is bound more than once in this parameter list.
-    IdentifierBoundMoreThanOnceInParameterList(Symbol),
+    IdentifierBoundMoreThanOnceInParameterList(Ident),
     /// Error E0416: identifier is bound more than once in the same pattern.
-    IdentifierBoundMoreThanOnceInSamePattern(Symbol),
+    IdentifierBoundMoreThanOnceInSamePattern(Ident),
     /// Error E0426: use of undeclared label.
     UndeclaredLabel { name: Symbol, suggestion: Option<LabelSuggestion> },
     /// Error E0429: `self` imports are only allowed within a `{ }` list.
@@ -292,14 +292,14 @@ enum ResolutionError<'ra> {
     UnreachableLabel { name: Symbol, definition_span: Span, suggestion: Option<LabelSuggestion> },
     /// Error E0323, E0324, E0325: mismatch between trait item and impl item.
     TraitImplMismatch {
-        name: Symbol,
+        name: Ident,
         kind: &'static str,
         trait_path: String,
         trait_item_span: Span,
         code: ErrCode,
     },
     /// Error E0201: multiple impl items for the same trait item.
-    TraitImplDuplicate { name: Symbol, trait_item_span: Span, old_span: Span },
+    TraitImplDuplicate { name: Ident, trait_item_span: Span, old_span: Span },
     /// Inline asm `sym` operand must refer to a `fn` or `static`.
     InvalidAsmSym,
     /// `self` used instead of `Self` in a generic parameter

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

@@ -13,7 +13,7 @@ use rustc_middle::ty::print::PrintTraitRefExt as _;
 use rustc_middle::ty::{self, GenericArgsRef, GenericParamDefKind, TyCtxt};
 use rustc_parse_format::{ParseMode, Parser, Piece, Position};
 use rustc_session::lint::builtin::UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES;
-use rustc_span::{Span, Symbol, kw, sym};
+use rustc_span::{Ident, Span, Symbol, kw, sym};
 use tracing::{debug, info};
 use {rustc_attr_parsing as attr, rustc_hir as hir};
 
@@ -375,7 +375,7 @@ impl IgnoredDiagnosticOption {
 #[help]
 pub struct UnknownFormatParameterForOnUnimplementedAttr {
     argument_name: Symbol,
-    trait_name: Symbol,
+    trait_name: Ident,
 }
 
 #[derive(LintDiagnostic)]
@@ -792,7 +792,7 @@ impl<'tcx> OnUnimplementedFormatString {
             tcx.trait_id_of_impl(item_def_id)
                 .expect("expected `on_unimplemented` to correspond to a trait")
         };
-        let trait_name = tcx.item_name(trait_def_id);
+        let trait_name = tcx.item_ident(trait_def_id);
         let generics = tcx.generics_of(item_def_id);
         let s = self.symbol.as_str();
         let mut parser = Parser::new(s, None, None, false, ParseMode::Format);
@@ -821,7 +821,11 @@ impl<'tcx> OnUnimplementedFormatString {
                         Position::ArgumentNamed(s) => {
                             match Symbol::intern(s) {
                                 // `{ThisTraitsName}` is allowed
-                                s if s == trait_name && !self.is_diagnostic_namespace_variant => (),
+                                s if s == trait_name.name
+                                    && !self.is_diagnostic_namespace_variant =>
+                                {
+                                    ()
+                                }
                                 s if ALLOWED_FORMAT_SYMBOLS.contains(&s)
                                     && !self.is_diagnostic_namespace_variant =>
                                 {