Auto merge of rust-lang#125410 - fmease:adj-lint-diag-api, r=nnethercote

[perf] Delay the construction of early lint diag structs

Attacks some of the perf regressions from rust-lang#124417 (comment).

See individual commits for details. The first three commits are not strictly necessary.
However, the 2nd one (06bc4fc, *Remove `LintDiagnostic::msg`*) makes the main change way nicer to implement.
It's also pretty sweet on its own if I may say so myself.

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -576,8 +576,8 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     lint::builtin::INLINE_NO_SANITIZE,
                     hir_id,
                     no_sanitize_span,
-                    "`no_sanitize` will have no effect after inlining",
                     |lint| {
+                        lint.primary_message("`no_sanitize` will have no effect after inlining");
                         lint.span_note(inline_span, "inlining requested here");
                     },
                 )

compiler/rustc_error_messages/src/lib.rs

@@ -364,17 +364,6 @@ impl From<Cow<'static, str>> for DiagMessage {
     }
 }
 
-/// A workaround for must_produce_diag ICEs when formatting types in disabled lints.
-///
-/// Delays formatting until `.into(): DiagMessage` is used.
-pub struct DelayDm<F>(pub F);
-
-impl<F: FnOnce() -> String> From<DelayDm<F>> for DiagMessage {
-    fn from(DelayDm(f): DelayDm<F>) -> Self {
-        DiagMessage::from(f())
-    }
-}
-
 /// Translating *into* a subdiagnostic message from a diagnostic message is a little strange - but
 /// the subdiagnostic functions (e.g. `span_label`) take a `SubdiagMessage` and the
 /// subdiagnostic derive refers to typed identifiers that are `DiagMessage`s, so need to be

compiler/rustc_errors/src/diagnostic.rs

@@ -200,8 +200,6 @@ pub trait SubdiagMessageOp<G: EmissionGuarantee> =
 pub trait LintDiagnostic<'a, G: EmissionGuarantee> {
     /// Decorate and emit a lint.
     fn decorate_lint<'b>(self, diag: &'b mut Diag<'a, G>);
-
-    fn msg(&self) -> DiagMessage;
 }
 
 #[derive(Clone, Debug, Encodable, Decodable)]

compiler/rustc_errors/src/lib.rs

@@ -39,7 +39,7 @@ pub use diagnostic_impls::{
 };
 pub use emitter::ColorConfig;
 pub use rustc_error_messages::{
-    fallback_fluent_bundle, fluent_bundle, DelayDm, DiagMessage, FluentBundle, LanguageIdentifier,
+    fallback_fluent_bundle, fluent_bundle, DiagMessage, FluentBundle, LanguageIdentifier,
     LazyFallbackBundle, MultiSpan, SpanLabel, SubdiagMessage,
 };
 pub use rustc_lint_defs::{pluralize, Applicability};
@@ -572,8 +572,8 @@ impl Drop for DiagCtxtInner {
             if let Some(backtrace) = &self.must_produce_diag {
                 panic!(
                     "must_produce_diag: `trimmed_def_paths` called but no diagnostics emitted; \
-                       use `DelayDm` for lints or `with_no_trimmed_paths` for debugging. \
-                       called at: {backtrace}"
+                     `with_no_trimmed_paths` for debugging. \
+                     called at: {backtrace}"
                 );
             }
         }

compiler/rustc_hir_analysis/src/check/check.rs

@@ -46,13 +46,9 @@ pub fn check_abi(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: Abi) {
             .emit();
         }
         None => {
-            tcx.node_span_lint(
-                UNSUPPORTED_CALLING_CONVENTIONS,
-                hir_id,
-                span,
-                "use of calling convention not supported on this target",
-                |_| {},
-            );
+            tcx.node_span_lint(UNSUPPORTED_CALLING_CONVENTIONS, hir_id, span, |lint| {
+                lint.primary_message("use of calling convention not supported on this target");
+            });
         }
     }
 
@@ -243,8 +239,8 @@ fn check_static_inhabited(tcx: TyCtxt<'_>, def_id: LocalDefId) {
             UNINHABITED_STATIC,
             tcx.local_def_id_to_hir_id(def_id),
             span,
-            "static of uninhabited type",
             |lint| {
+                lint.primary_message("static of uninhabited type");
                 lint
                 .note("uninhabited statics cannot be initialized, and any access would be an immediate error");
             },
@@ -1310,9 +1306,11 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
                     REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
                     tcx.local_def_id_to_hir_id(adt.did().expect_local()),
                     span,
-                    "zero-sized fields in `repr(transparent)` cannot \
-                    contain external non-exhaustive types",
                     |lint| {
+                        lint.primary_message(
+                            "zero-sized fields in `repr(transparent)` cannot \
+                             contain external non-exhaustive types",
+                        );
                         let note = if non_exhaustive {
                             "is marked with `#[non_exhaustive]`"
                         } else {

compiler/rustc_hir_analysis/src/check/intrinsicck.rs

@@ -281,8 +281,8 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                     lint::builtin::ASM_SUB_REGISTER,
                     expr.hir_id,
                     spans,
-                    "formatting may not be suitable for sub-register argument",
                     |lint| {
+                        lint.primary_message("formatting may not be suitable for sub-register argument");
                         lint.span_label(expr.span, "for this argument");
                         lint.help(format!(
                             "use `{{{idx}:{suggested_modifier}}}` to have the register formatted as `{suggested_result}` (for {suggested_size}-bit values)",

compiler/rustc_hir_analysis/src/check_unused.rs

@@ -35,11 +35,12 @@ fn check_unused_traits(tcx: TyCtxt<'_>, (): ()) {
             continue;
         }
         let (path, _) = item.expect_use();
-        let msg = if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(path.span) {
-            format!("unused import: `{snippet}`")
-        } else {
-            "unused import".to_owned()
-        };
-        tcx.node_span_lint(lint::builtin::UNUSED_IMPORTS, item.hir_id(), path.span, msg, |_| {});
+        tcx.node_span_lint(lint::builtin::UNUSED_IMPORTS, item.hir_id(), path.span, |lint| {
+            if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(path.span) {
+                lint.primary_message(format!("unused import: `{snippet}`"));
+            } else {
+                lint.primary_message("unused import");
+            }
+        });
     }
 }

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -317,8 +317,9 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                             lint::builtin::INVALID_TYPE_PARAM_DEFAULT,
                             param.hir_id,
                             param.span,
-                            TYPE_DEFAULT_NOT_ALLOWED,
-                            |_| {},
+                            |lint| {
+                                lint.primary_message(TYPE_DEFAULT_NOT_ALLOWED);
+                            },
                         );
                     }
                     Defaults::Deny => {

compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs

@@ -646,8 +646,9 @@ pub(crate) fn prohibit_explicit_late_bound_lifetimes(
                 LATE_BOUND_LIFETIME_ARGUMENTS,
                 args.args[0].hir_id(),
                 multispan,
-                msg,
-                |_| {},
+                |lint| {
+                    lint.primary_message(msg);
+                },
             );
         }
 

compiler/rustc_hir_analysis/src/hir_ty_lowering/lint.rs

@@ -72,8 +72,8 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             self.maybe_suggest_assoc_ty_bound(self_ty, &mut diag);
             diag.stash(self_ty.span, StashKey::TraitMissingMethod);
         } else {
-            let msg = "trait objects without an explicit `dyn` are deprecated";
-            tcx.node_span_lint(BARE_TRAIT_OBJECTS, self_ty.hir_id, self_ty.span, msg, |lint| {
+            tcx.node_span_lint(BARE_TRAIT_OBJECTS, self_ty.hir_id, self_ty.span, |lint| {
+                lint.primary_message("trait objects without an explicit `dyn` are deprecated");
                 if self_ty.span.can_be_used_for_suggestions() {
                     lint.multipart_suggestion_verbose(
                         "if this is an object-safe trait, use `dyn`",

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -1165,33 +1165,28 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         let ty = self.lower_assoc_ty(span, assoc_ty_did, assoc_segment, bound);
 
         if let Some(variant_def_id) = variant_resolution {
-            tcx.node_span_lint(
-                AMBIGUOUS_ASSOCIATED_ITEMS,
-                hir_ref_id,
-                span,
-                "ambiguous associated item",
-                |lint| {
-                    let mut could_refer_to = |kind: DefKind, def_id, also| {
-                        let note_msg = format!(
-                            "`{}` could{} refer to the {} defined here",
-                            assoc_ident,
-                            also,
-                            tcx.def_kind_descr(kind, def_id)
-                        );
-                        lint.span_note(tcx.def_span(def_id), note_msg);
-                    };
+            tcx.node_span_lint(AMBIGUOUS_ASSOCIATED_ITEMS, hir_ref_id, span, |lint| {
+                lint.primary_message("ambiguous associated item");
+                let mut could_refer_to = |kind: DefKind, def_id, also| {
+                    let note_msg = format!(
+                        "`{}` could{} refer to the {} defined here",
+                        assoc_ident,
+                        also,
+                        tcx.def_kind_descr(kind, def_id)
+                    );
+                    lint.span_note(tcx.def_span(def_id), note_msg);
+                };
 
-                    could_refer_to(DefKind::Variant, variant_def_id, "");
-                    could_refer_to(DefKind::AssocTy, assoc_ty_did, " also");
+                could_refer_to(DefKind::Variant, variant_def_id, "");
+                could_refer_to(DefKind::AssocTy, assoc_ty_did, " also");
 
-                    lint.span_suggestion(
-                        span,
-                        "use fully-qualified syntax",
-                        format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident),
-                        Applicability::MachineApplicable,
-                    );
-                },
-            );
+                lint.span_suggestion(
+                    span,
+                    "use fully-qualified syntax",
+                    format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident),
+                    Applicability::MachineApplicable,
+                );
+            });
         }
         Ok((ty, DefKind::AssocTy, assoc_ty_did))
     }

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -64,19 +64,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 debug!("warn_if_unreachable: id={:?} span={:?} kind={}", id, span, kind);
 
                 let msg = format!("unreachable {kind}");
-                self.tcx().node_span_lint(
-                    lint::builtin::UNREACHABLE_CODE,
-                    id,
-                    span,
-                    msg.clone(),
-                    |lint| {
-                        lint.span_label(span, msg).span_label(
-                            orig_span,
-                            custom_note
-                                .unwrap_or("any code following this expression is unreachable"),
-                        );
-                    },
-                )
+                self.tcx().node_span_lint(lint::builtin::UNREACHABLE_CODE, id, span, |lint| {
+                    lint.primary_message(msg.clone());
+                    lint.span_label(span, msg).span_label(
+                        orig_span,
+                        custom_note.unwrap_or("any code following this expression is unreachable"),
+                    );
+                })
             }
         }
     }