diagnostics: if AssocFn has self argument, describe as method

Discussed in
https://rust-lang.zulipchat.com/#narrow/stream/147480-t-compiler.2Fwg-diagnostics/topic/.22associated.20function.22.20vs.20.22method.22/near/329265515

This commit also changes the tooltips on rustdoc intra-doc links
targeting methods.

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -2135,7 +2135,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
         let tcx = self.infcx.tcx;
 
-        let (_, escapes_from) = tcx.article_and_description(self.mir_def_id().to_def_id());
+        let escapes_from = tcx.def_descr(self.mir_def_id().to_def_id());
 
         let mut err =
             borrowck_errors::borrowed_data_escapes_closure(tcx, escape_span, escapes_from);

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -660,10 +660,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             errci.outlived_fr,
         );
 
-        let (_, escapes_from) = self
-            .infcx
-            .tcx
-            .article_and_description(self.regioncx.universal_regions().defining_ty.def_id());
+        let escapes_from =
+            self.infcx.tcx.def_descr(self.regioncx.universal_regions().defining_ty.def_id());
 
         // Revert to the normal error in these cases.
         // Assignments aren't "escapes" in function items.
@@ -757,8 +755,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             ..
         } = errci;
 
-        let (_, mir_def_name) =
-            self.infcx.tcx.article_and_description(self.mir_def_id().to_def_id());
+        let mir_def_name = self.infcx.tcx.def_descr(self.mir_def_id().to_def_id());
 
         let err = LifetimeOutliveErr { span: *span };
         let mut diag = self.infcx.tcx.sess.create_err(err);

compiler/rustc_hir/src/def.rs

@@ -124,6 +124,11 @@ pub enum DefKind {
 }
 
 impl DefKind {
+    /// Get an English description for the item's kind.
+    ///
+    /// If you have access to `TyCtxt`, use `TyCtxt::def_descr` or
+    /// `TyCtxt::def_kind_descr` instead, because they give better
+    /// information for generators and associated functions.
     pub fn descr(self, def_id: DefId) -> &'static str {
         match self {
             DefKind::Fn => "function",
@@ -166,6 +171,10 @@ impl DefKind {
     }
 
     /// Gets an English article for the definition.
+    ///
+    /// If you have access to `TyCtxt`, use `TyCtxt::def_descr_article` or
+    /// `TyCtxt::def_kind_descr_article` instead, because they give better
+    /// information for generators and associated functions.
     pub fn article(&self) -> &'static str {
         match *self {
             DefKind::AssocTy

compiler/rustc_hir_analysis/src/astconv/errors.rs

@@ -304,10 +304,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             if let Some(did) = adt_did {
                 err.span_label(
                     tcx.def_span(did),
-                    format!(
-                        "associated item `{name}` not found for this {}",
-                        tcx.def_kind(did).descr(did)
-                    ),
+                    format!("associated item `{name}` not found for this {}", tcx.def_descr(did)),
                 );
             }
         };

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -1217,7 +1217,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     | (hir::def::DefKind::AssocConst, ty::TermKind::Const(_)) => (),
                     (_, _) => {
                         let got = if let Some(_) = term.ty() { "type" } else { "constant" };
-                        let expected = def_kind.descr(assoc_item_def_id);
+                        let expected = tcx.def_descr(assoc_item_def_id);
                         let mut err = tcx.sess.struct_span_err(
                             binding.span,
                             &format!("expected {expected} bound, found {got}"),
@@ -1552,7 +1552,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         i.bottom().1,
                         E0038,
                         "the {} `{}` cannot be made into an object",
-                        tcx.def_kind(def_id).descr(def_id),
+                        tcx.def_descr(def_id),
                         tcx.item_name(def_id),
                     );
                     err.note(
@@ -2174,7 +2174,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             "`{}` could{} refer to the {} defined here",
                             assoc_ident,
                             also,
-                            kind.descr(def_id)
+                            tcx.def_kind_descr(kind, def_id)
                         );
                         lint.span_note(tcx.def_span(def_id), &note_msg);
                     };
@@ -2350,7 +2350,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let kind = DefKind::AssocTy;
 
         if !tcx.visibility(item).is_accessible_from(def_scope, tcx) {
-            let kind = kind.descr(item);
+            let kind = tcx.def_kind_descr(kind, item);
             let msg = format!("{kind} `{name}` is private");
             let def_span = tcx.def_span(item);
             tcx.sess

compiler/rustc_hir_analysis/src/check/check.rs

@@ -1460,7 +1460,7 @@ fn opaque_type_cycle_error(
                                     span,
                                     format!(
                                         "{} captures itself here",
-                                        tcx.def_kind(closure_def_id).descr(closure_def_id)
+                                        tcx.def_descr(closure_def_id)
                                     ),
                                 );
                             }

compiler/rustc_hir_analysis/src/check/dropck.rs

@@ -71,7 +71,7 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>(
 
     let drop_impl_span = tcx.def_span(drop_impl_did);
     let item_span = tcx.def_span(self_type_did);
-    let self_descr = tcx.def_kind(self_type_did).descr(self_type_did);
+    let self_descr = tcx.def_descr(self_type_did);
     let mut err =
         struct_span_err!(tcx.sess, drop_impl_span, E0366, "`Drop` impls cannot be specialized");
     match arg {
@@ -217,7 +217,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
 
         if !assumptions_in_impl_context.iter().copied().any(predicate_matches_closure) {
             let item_span = tcx.def_span(self_type_did);
-            let self_descr = tcx.def_kind(self_type_did).descr(self_type_did.to_def_id());
+            let self_descr = tcx.def_descr(self_type_did.to_def_id());
             let reported = struct_span_err!(
                 tcx.sess,
                 predicate_sp,

compiler/rustc_hir_analysis/src/coherence/orphan.rs

@@ -531,7 +531,7 @@ fn lint_auto_trait_impl<'tcx>(
         }),
         |lint| {
             let item_span = tcx.def_span(self_type_did);
-            let self_descr = tcx.def_kind(self_type_did).descr(self_type_did);
+            let self_descr = tcx.def_descr(self_type_did);
             match arg {
                 ty::util::NotUniqueParam::DuplicateParam(arg) => {
                     lint.note(&format!("`{}` is mentioned multiple times", arg));

compiler/rustc_hir_analysis/src/structured_errors/wrong_number_of_generic_args.rs

@@ -439,7 +439,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
 
     fn create_error_message(&self) -> String {
         let def_path = self.tcx.def_path_str(self.def_id);
-        let def_kind = self.tcx.def_kind(self.def_id).descr(self.def_id);
+        let def_kind = self.tcx.def_descr(self.def_id);
         let (quantifier, bound) = self.get_quantifier_and_bound();
         let kind = self.kind();
         let provided_lt_args = self.num_provided_lifetime_args();
@@ -990,7 +990,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
         };
 
         let msg = {
-            let def_kind = self.tcx.def_kind(self.def_id).descr(self.def_id);
+            let def_kind = self.tcx.def_descr(self.def_id);
             let (quantifier, bound) = self.get_quantifier_and_bound();
 
             let params = if bound == 0 {

compiler/rustc_hir_typeck/src/callee.rs

@@ -671,7 +671,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 && !self.type_is_sized_modulo_regions(self.param_env, output_ty, callee_expr.span)
             {
                 let descr = match maybe_def {
-                    DefIdOrName::DefId(def_id) => self.tcx.def_kind(def_id).descr(def_id),
+                    DefIdOrName::DefId(def_id) => self.tcx.def_descr(def_id),
                     DefIdOrName::Name(name) => name,
                 };
                 err.span_label(

compiler/rustc_hir_typeck/src/expr.rs

@@ -2448,7 +2448,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         return_ty: Option<Ty<'tcx>>,
     ) {
         let struct_path = self.tcx().def_path_str(base_did);
-        let kind_name = self.tcx().def_kind(base_did).descr(base_did);
+        let kind_name = self.tcx().def_descr(base_did);
         let mut err = struct_span_err!(
             self.tcx().sess,
             field.span,

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1938,8 +1938,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 spans.push_span_label(param.span, "");
             }
 
-            let def_kind = self.tcx.def_kind(def_id);
-            err.span_note(spans, &format!("{} defined here", def_kind.descr(def_id)));
+            err.span_note(spans, &format!("{} defined here", self.tcx.def_descr(def_id)));
         } else if let Some(hir::Node::Expr(e)) = self.tcx.hir().get_if_local(def_id)
             && let hir::ExprKind::Closure(hir::Closure { body, .. }) = &e.kind
         {
@@ -1952,10 +1951,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             };
             err.span_note(span, &format!("{} defined here", kind));
         } else {
-            let def_kind = self.tcx.def_kind(def_id);
             err.span_note(
                 self.tcx.def_span(def_id),
-                &format!("{} defined here", def_kind.descr(def_id)),
+                &format!("{} defined here", self.tcx.def_descr(def_id)),
             );
         }
     }

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -120,7 +120,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 DefIdOrName::DefId(def_id) => match self.tcx.def_kind(def_id) {
                     DefKind::Ctor(CtorOf::Struct, _) => "construct this tuple struct".to_string(),
                     DefKind::Ctor(CtorOf::Variant, _) => "construct this tuple variant".to_string(),
-                    kind => format!("call this {}", kind.descr(def_id)),
+                    kind => format!("call this {}", self.tcx.def_kind_descr(kind, def_id)),
                 },
                 DefIdOrName::Name(name) => format!("call this {name}"),
             };
@@ -339,7 +339,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     CtorOf::Variant => "an enum variant",
                 }));
             } else {
-                let descr = kind.descr(def_id);
+                let descr = self.tcx.def_kind_descr(kind, def_id);
                 err.span_label(sp, format!("{descr} `{name}` defined here"));
             }
             return true;

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1366,8 +1366,8 @@ impl<'tcx> Pick<'tcx> {
             span,
             format!(
                 "{} {} with this name may be added to the standard library in the future",
-                def_kind.article(),
-                def_kind.descr(self.item.def_id),
+                tcx.def_kind_descr_article(def_kind, self.item.def_id),
+                tcx.def_kind_descr(def_kind, self.item.def_id),
             ),
             |lint| {
                 match (self.item.kind, self.item.container) {

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -160,7 +160,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
 
             MethodError::PrivateMatch(kind, def_id, out_of_scope_traits) => {
-                let kind = kind.descr(def_id);
+                let kind = self.tcx.def_kind_descr(kind, def_id);
                 let mut err = struct_span_err!(
                     self.tcx.sess,
                     item_name.span,
@@ -1062,8 +1062,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         span,
                         &format!(
                             "there is {} {} with a similar name",
-                            def_kind.article(),
-                            def_kind.descr(similar_candidate.def_id),
+                            self.tcx.def_kind_descr_article(def_kind, similar_candidate.def_id),
+                            self.tcx.def_kind_descr(def_kind, similar_candidate.def_id)
                         ),
                         similar_candidate.name,
                         Applicability::MaybeIncorrect,
@@ -1172,7 +1172,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             path,
                             ty,
                             item.kind,
-                            item.def_id,
+                            self.tcx.def_kind_descr(item.kind.as_def_kind(), item.def_id),
                             sugg_span,
                             idx,
                             self.tcx.sess.source_map(),
@@ -1208,7 +1208,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             path,
                             rcvr_ty,
                             item.kind,
-                            item.def_id,
+                            self.tcx.def_kind_descr(item.kind.as_def_kind(), item.def_id),
                             sugg_span,
                             idx,
                             self.tcx.sess.source_map(),
@@ -2853,7 +2853,7 @@ fn print_disambiguation_help<'tcx>(
     trait_name: String,
     rcvr_ty: Ty<'_>,
     kind: ty::AssocKind,
-    def_id: DefId,
+    def_kind_descr: &'static str,
     span: Span,
     candidate: Option<usize>,
     source_map: &source_map::SourceMap,
@@ -2886,7 +2886,7 @@ fn print_disambiguation_help<'tcx>(
         span,
         &format!(
             "disambiguate the {} for {}",
-            kind.as_def_kind().descr(def_id),
+            def_kind_descr,
             if let Some(candidate) = candidate {
                 format!("candidate #{}", candidate)
             } else {

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -122,7 +122,7 @@ impl InferenceDiagnosticsParentData {
             tcx.def_key(parent_def_id).disambiguated_data.data.get_opt_name()?.to_string();
 
         Some(InferenceDiagnosticsParentData {
-            prefix: tcx.def_kind(parent_def_id).descr(parent_def_id),
+            prefix: tcx.def_descr(parent_def_id),
             name: parent_name,
         })
     }

compiler/rustc_middle/src/middle/stability.rs

@@ -255,7 +255,7 @@ fn late_report_deprecation(
     let method_span = method_span.unwrap_or(span);
     tcx.struct_span_lint_hir(lint, hir_id, method_span, message, |diag| {
         if let hir::Node::Expr(_) = tcx.hir().get(hir_id) {
-            let kind = tcx.def_kind(def_id).descr(def_id);
+            let kind = tcx.def_descr(def_id);
             deprecation_suggestion(diag, kind, suggestion, method_span);
         }
         diag
@@ -392,7 +392,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     let lint = deprecation_lint(is_in_effect);
                     if self.lint_level_at_node(lint, id).0 != Level::Allow {
                         let def_path = with_no_trimmed_paths!(self.def_path_str(def_id));
-                        let def_kind = self.def_kind(def_id).descr(def_id);
+                        let def_kind = self.def_descr(def_id);
 
                         late_report_deprecation(
                             self,

compiler/rustc_middle/src/ty/context.rs

@@ -1200,13 +1200,8 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Returns a displayable description and article for the given `def_id` (e.g. `("a", "struct")`).
     pub fn article_and_description(self, def_id: DefId) -> (&'static str, &'static str) {
-        match self.def_kind(def_id) {
-            DefKind::Generator => match self.generator_kind(def_id).unwrap() {
-                rustc_hir::GeneratorKind::Async(..) => ("an", "async closure"),
-                rustc_hir::GeneratorKind::Gen => ("a", "generator"),
-            },
-            def_kind => (def_kind.article(), def_kind.descr(def_id)),
-        }
+        let kind = self.def_kind(def_id);
+        (self.def_kind_descr_article(kind, def_id), self.def_kind_descr(kind, def_id))
     }
 
     pub fn type_length_limit(self) -> Limit {

compiler/rustc_middle/src/ty/util.rs

@@ -761,6 +761,40 @@ impl<'tcx> TyCtxt<'tcx> {
         }
         (generator_layout, generator_saved_local_names)
     }
+
+    /// Query and get an English description for the item's kind.
+    pub fn def_descr(self, def_id: DefId) -> &'static str {
+        self.def_kind_descr(self.def_kind(def_id), def_id)
+    }
+
+    /// Get an English description for the item's kind.
+    pub fn def_kind_descr(self, def_kind: DefKind, def_id: DefId) -> &'static str {
+        match def_kind {
+            DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "method",
+            DefKind::Generator => match self.generator_kind(def_id).unwrap() {
+                rustc_hir::GeneratorKind::Async(..) => "async closure",
+                rustc_hir::GeneratorKind::Gen => "generator",
+            },
+            _ => def_kind.descr(def_id),
+        }
+    }
+
+    /// Gets an English article for the [`TyCtxt::def_descr`].
+    pub fn def_descr_article(self, def_id: DefId) -> &'static str {
+        self.def_kind_descr_article(self.def_kind(def_id), def_id)
+    }
+
+    /// Gets an English article for the [`TyCtxt::def_kind_descr`].
+    pub fn def_kind_descr_article(self, def_kind: DefKind, def_id: DefId) -> &'static str {
+        match def_kind {
+            DefKind::AssocFn if self.associated_item(def_id).fn_has_self_parameter => "a",
+            DefKind::Generator => match self.generator_kind(def_id).unwrap() {
+                rustc_hir::GeneratorKind::Async(..) => "an",
+                rustc_hir::GeneratorKind::Gen => "a",
+            },
+            _ => def_kind.article(),
+        }
+    }
 }
 
 struct OpaqueTypeExpander<'tcx> {

compiler/rustc_passes/src/dead.rs

@@ -691,7 +691,7 @@ impl<'tcx> DeadVisitor<'tcx> {
             })
             .collect();
 
-        let descr = tcx.def_kind(first_id).descr(first_id.to_def_id());
+        let descr = tcx.def_descr(first_id.to_def_id());
         let num = dead_codes.len();
         let multiple = num > 6;
         let name_list = names.into();
@@ -703,7 +703,7 @@ impl<'tcx> DeadVisitor<'tcx> {
         };
 
         let parent_info = if let Some(parent_item) = parent_item {
-            let parent_descr = tcx.def_kind(parent_item).descr(parent_item.to_def_id());
+            let parent_descr = tcx.def_descr(parent_item.to_def_id());
             Some(ParentInfo {
                 num,
                 descr,