Use get_diagnostic_name more

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -742,15 +742,13 @@ impl BorrowedContentSource<'tcx> {
             BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
             BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
             BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
-            BorrowedContentSource::OverloadedDeref(ty) => match ty.kind() {
-                ty::Adt(def, _) if tcx.is_diagnostic_item(sym::Rc, def.did) => {
-                    "an `Rc`".to_string()
-                }
-                ty::Adt(def, _) if tcx.is_diagnostic_item(sym::Arc, def.did) => {
-                    "an `Arc`".to_string()
-                }
-                _ => format!("dereference of `{}`", ty),
-            },
+            BorrowedContentSource::OverloadedDeref(ty) => ty
+                .ty_adt_def()
+                .and_then(|adt| match tcx.get_diagnostic_name(adt.did)? {
+                    name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
+                    _ => None,
+                })
+                .unwrap_or_else(|| format!("dereference of `{}`", ty)),
             BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{}`", ty),
         }
     }
@@ -774,15 +772,13 @@ impl BorrowedContentSource<'tcx> {
             BorrowedContentSource::DerefMutableRef => {
                 bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
             }
-            BorrowedContentSource::OverloadedDeref(ty) => match ty.kind() {
-                ty::Adt(def, _) if tcx.is_diagnostic_item(sym::Rc, def.did) => {
-                    "an `Rc`".to_string()
-                }
-                ty::Adt(def, _) if tcx.is_diagnostic_item(sym::Arc, def.did) => {
-                    "an `Arc`".to_string()
-                }
-                _ => format!("a dereference of `{}`", ty),
-            },
+            BorrowedContentSource::OverloadedDeref(ty) => ty
+                .ty_adt_def()
+                .and_then(|adt| match tcx.get_diagnostic_name(adt.did)? {
+                    name @ (sym::Rc | sym::Arc) => Some(format!("an `{}`", name)),
+                    _ => None,
+                })
+                .unwrap_or_else(|| format!("dereference of `{}`", ty)),
             BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{}`", ty),
         }
     }
@@ -966,8 +962,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         _ => None,
                     });
                 let is_option_or_result = parent_self_ty.map_or(false, |def_id| {
-                    tcx.is_diagnostic_item(sym::Option, def_id)
-                        || tcx.is_diagnostic_item(sym::Result, def_id)
+                    matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result))
                 });
                 FnSelfUseKind::Normal { self_arg, implicit_into_iter, is_option_or_result }
             });

compiler/rustc_lint/src/enum_intrinsics_non_enums.rs

@@ -91,16 +91,14 @@ fn enforce_mem_variant_count(cx: &LateContext<'_>, func_expr: &hir::Expr<'_>, sp
 
 impl<'tcx> LateLintPass<'tcx> for EnumIntrinsicsNonEnums {
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
-        if let hir::ExprKind::Call(ref func, ref args) = expr.kind {
-            if let hir::ExprKind::Path(ref qpath) = func.kind {
-                if let Some(def_id) = cx.qpath_res(qpath, func.hir_id).opt_def_id() {
-                    if cx.tcx.is_diagnostic_item(sym::mem_discriminant, def_id) {
-                        enforce_mem_discriminant(cx, func, expr.span, args[0].span);
-                    } else if cx.tcx.is_diagnostic_item(sym::mem_variant_count, def_id) {
-                        enforce_mem_variant_count(cx, func, expr.span);
-                    }
-                }
-            }
+        let hir::ExprKind::Call(func, args) = &expr.kind else { return };
+        let hir::ExprKind::Path(qpath) = &func.kind else { return };
+        let Some(def_id) = cx.qpath_res(qpath, func.hir_id).opt_def_id() else { return };
+        let Some(name) = cx.tcx.get_diagnostic_name(def_id) else { return };
+        match name {
+            sym::mem_discriminant => enforce_mem_discriminant(cx, func, expr.span, args[0].span),
+            sym::mem_variant_count => enforce_mem_variant_count(cx, func, expr.span),
+            _ => {}
         }
     }
 }

compiler/rustc_lint/src/lib.rs

@@ -33,6 +33,7 @@
 #![cfg_attr(bootstrap, feature(format_args_capture))]
 #![feature(iter_order_by)]
 #![feature(iter_zip)]
+#![feature(let_else)]
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(control_flow_enum)]

compiler/rustc_lint/src/non_fmt_panic.rs

@@ -309,14 +309,21 @@ fn panic_call<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>) -> (Span,
     // Unwrap more levels of macro expansion, as panic_2015!()
     // was likely expanded from panic!() and possibly from
     // [debug_]assert!().
-    for &i in
-        &[sym::std_panic_macro, sym::core_panic_macro, sym::assert_macro, sym::debug_assert_macro]
-    {
+    loop {
         let parent = expn.call_site.ctxt().outer_expn_data();
-        if parent.macro_def_id.map_or(false, |id| cx.tcx.is_diagnostic_item(i, id)) {
-            expn = parent;
-            panic_macro = i;
+        let Some(id) = parent.macro_def_id else { break };
+        let Some(name) = cx.tcx.get_diagnostic_name(id) else { break };
+        if !matches!(
+            name,
+            sym::core_panic_macro
+                | sym::std_panic_macro
+                | sym::assert_macro
+                | sym::debug_assert_macro
+        ) {
+            break;
         }
+        expn = parent;
+        panic_macro = name;
     }
 
     let macro_symbol =

compiler/rustc_lint/src/noop_method_call.rs

@@ -75,38 +75,36 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
             _ => return,
         };
         // (Re)check that it implements the noop diagnostic.
-        for s in [sym::noop_method_clone, sym::noop_method_deref, sym::noop_method_borrow].iter() {
-            if cx.tcx.is_diagnostic_item(*s, i.def_id()) {
-                let method = &call.ident.name;
-                let receiver = &elements[0];
-                let receiver_ty = cx.typeck_results().expr_ty(receiver);
-                let expr_ty = cx.typeck_results().expr_ty_adjusted(expr);
-                if receiver_ty != expr_ty {
-                    // This lint will only trigger if the receiver type and resulting expression \
-                    // type are the same, implying that the method call is unnecessary.
-                    return;
-                }
-                let expr_span = expr.span;
-                let note = format!(
-                    "the type `{:?}` which `{}` is being called on is the same as \
-                     the type returned from `{}`, so the method call does not do \
-                     anything and can be removed",
-                    receiver_ty, method, method,
-                );
-
-                let span = expr_span.with_lo(receiver.span.hi());
-                cx.struct_span_lint(NOOP_METHOD_CALL, span, |lint| {
-                    let method = &call.ident.name;
-                    let message = format!(
-                        "call to `.{}()` on a reference in this situation does nothing",
-                        &method,
-                    );
-                    lint.build(&message)
-                        .span_label(span, "unnecessary method call")
-                        .note(&note)
-                        .emit()
-                });
-            }
+        let Some(name) = cx.tcx.get_diagnostic_name(i.def_id()) else { return };
+        if !matches!(
+            name,
+            sym::noop_method_borrow | sym::noop_method_clone | sym::noop_method_deref
+        ) {
+            return;
         }
+        let method = &call.ident.name;
+        let receiver = &elements[0];
+        let receiver_ty = cx.typeck_results().expr_ty(receiver);
+        let expr_ty = cx.typeck_results().expr_ty_adjusted(expr);
+        if receiver_ty != expr_ty {
+            // This lint will only trigger if the receiver type and resulting expression \
+            // type are the same, implying that the method call is unnecessary.
+            return;
+        }
+        let expr_span = expr.span;
+        let note = format!(
+            "the type `{:?}` which `{}` is being called on is the same as \
+             the type returned from `{}`, so the method call does not do \
+             anything and can be removed",
+            receiver_ty, method, method,
+        );
+
+        let span = expr_span.with_lo(receiver.span.hi());
+        cx.struct_span_lint(NOOP_METHOD_CALL, span, |lint| {
+            let method = &call.ident.name;
+            let message =
+                format!("call to `.{}()` on a reference in this situation does nothing", &method,);
+            lint.build(&message).span_label(span, "unnecessary method call").note(&note).emit()
+        });
     }
 }

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

@@ -539,11 +539,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                         // is otherwise overwhelming and unhelpful (see #85844 for an
                         // example).
 
-                        let trait_is_debug =
-                            self.tcx.is_diagnostic_item(sym::Debug, trait_ref.def_id());
-                        let trait_is_display =
-                            self.tcx.is_diagnostic_item(sym::Display, trait_ref.def_id());
-
                         let in_std_macro =
                             match obligation.cause.span.ctxt().outer_expn_data().macro_def_id {
                                 Some(macro_def_id) => {
@@ -553,7 +548,12 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                                 None => false,
                             };
 
-                        if in_std_macro && (trait_is_debug || trait_is_display) {
+                        if in_std_macro
+                            && matches!(
+                                self.tcx.get_diagnostic_name(trait_ref.def_id()),
+                                Some(sym::Debug | sym::Display)
+                            )
+                        {
                             err.emit();
                             return;
                         }