Rollup merge of #118727 - compiler-errors:lint-decorate, r=WaffleLapkin

Don't pass lint back out of lint decorator

Change the decorator function in the signature of the `emit_lint`/`span_lint`/etc family of methods from `impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>) -> &'b mut DiagnosticBuilder<'a, ()>` to `impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>)`. I consider it easier to read this way, especially when there's control flow involved.

r? nnethercote though feel free to reassign

38 files changed, 53 insertions, 153 deletions

diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 40a985cf255..015ea10d721 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -578,7 +578,9 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     hir_id,
                     no_sanitize_span,
                     "`no_sanitize` will have no effect after inlining",
-                    |lint| lint.span_note(inline_span, "inlining requested here"),
+                    |lint| {
+                        lint.span_note(inline_span, "inlining requested here");
+                    },
                 )
             }
         }
diff --git a/compiler/rustc_hir_analysis/src/astconv/generics.rs b/compiler/rustc_hir_analysis/src/astconv/generics.rs
index 47fbed45b91..be73c027fdc 100644
--- a/compiler/rustc_hir_analysis/src/astconv/generics.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/generics.rs
@@ -661,7 +661,7 @@ pub(crate) fn prohibit_explicit_late_bound_lifetimes(
                 args.args[0].hir_id(),
                 multispan,
                 msg,
-                |lint| lint,
+                |_| {},
             );
         }
 
diff --git a/compiler/rustc_hir_analysis/src/astconv/lint.rs b/compiler/rustc_hir_analysis/src/astconv/lint.rs
index 43d4248ab74..9afb04b7470 100644
--- a/compiler/rustc_hir_analysis/src/astconv/lint.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/lint.rs
@@ -122,7 +122,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             Applicability::MachineApplicable,
                         );
                         self.maybe_lint_blanket_trait_impl(self_ty, lint);
-                        lint
                     },
                 );
             }
diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs
index 9743c9a3d7b..6f8e80172dd 100644
--- a/compiler/rustc_hir_analysis/src/astconv/mod.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs
@@ -1434,8 +1434,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident),
                         Applicability::MachineApplicable,
                     );
-
-                    lint
                 },
             );
         }
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index e6245e4d0b1..8413a1cc0db 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -51,7 +51,7 @@ pub fn check_abi(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: Abi) {
                 hir_id,
                 span,
                 "use of calling convention not supported on this target",
-                |lint| lint,
+                |_| {},
             );
         }
     }
@@ -190,7 +190,7 @@ fn check_static_inhabited(tcx: TyCtxt<'_>, def_id: LocalDefId) {
             "static of uninhabited type",
             |lint| {
                 lint
-                .note("uninhabited statics cannot be initialized, and any access would be an immediate error")
+                .note("uninhabited statics cannot be initialized, and any access would be an immediate error");
             },
         );
     }
@@ -1093,7 +1093,7 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
                             "this {descr} contains `{field_ty}`, which {note}, \
                                 and makes it not a breaking change to become \
                                 non-zero-sized in the future."
-                        ))
+                        ));
                     },
                 )
             } else {
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 4705d9350b0..18d9963aaa4 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -574,7 +574,6 @@ fn emit_implied_wf_lint<'tcx>(
                     Applicability::MaybeIncorrect,
                 );
             }
-            lint
         },
     );
 }
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsicck.rs b/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
index 7c9624206e5..d86ebc2c9c3 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
@@ -276,7 +276,6 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                         lint.help(format!(
                             "or use `{{{idx}:{default_modifier}}}` to keep the default formatting of `{default_result}`",
                         ));
-                        lint
                     },
                 );
             }
diff --git a/compiler/rustc_hir_analysis/src/check_unused.rs b/compiler/rustc_hir_analysis/src/check_unused.rs
index 9ad73eeffc6..36cb8f7a202 100644
--- a/compiler/rustc_hir_analysis/src/check_unused.rs
+++ b/compiler/rustc_hir_analysis/src/check_unused.rs
@@ -45,7 +45,7 @@ fn check_unused_traits(tcx: TyCtxt<'_>, (): ()) {
             item.hir_id(),
             path.span,
             msg,
-            |lint| lint,
+            |_| {},
         );
     }
 }
diff --git a/compiler/rustc_hir_analysis/src/coherence/orphan.rs b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
index 45100457629..88128d22a3d 100644
--- a/compiler/rustc_hir_analysis/src/coherence/orphan.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
@@ -522,7 +522,7 @@ fn lint_auto_trait_impl<'tcx>(
                 format!(
                     "try using the same sequence of generic parameters as the {self_descr} definition",
                 ),
-            )
+            );
         },
     );
 }
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index c1c2bb62c66..3ee2822edd8 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -279,7 +279,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                             param.hir_id,
                             param.span,
                             TYPE_DEFAULT_NOT_ALLOWED,
-                            |lint| lint,
+                            |_| {},
                         );
                     }
                     Defaults::Deny => {
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 5dcf3fe20f1..a1aac4df932 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -925,7 +925,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                                     "you can use the `'static` lifetime directly, in place of `{}`",
                                     lifetime.ident,
                                 );
-                                lint.help(help)
+                                lint.help(help);
                             },
                         );
                     }
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 7744f75121e..3bee42eb89c 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -72,7 +72,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             orig_span,
                             custom_note
                                 .unwrap_or("any code following this expression is unreachable"),
-                        )
+                        );
                     },
                 )
             }
diff --git a/compiler/rustc_hir_typeck/src/method/prelude2021.rs b/compiler/rustc_hir_typeck/src/method/prelude2021.rs
index 3f1dca5b1de..43d258de6ca 100644
--- a/compiler/rustc_hir_typeck/src/method/prelude2021.rs
+++ b/compiler/rustc_hir_typeck/src/method/prelude2021.rs
@@ -122,8 +122,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             format!("disambiguate the method call with `({self_adjusted})`",),
                         );
                     }
-
-                    lint
                 },
             );
         } else {
@@ -187,8 +185,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             ),
                         );
                     }
-
-                    lint
                 },
             );
         }
@@ -307,8 +303,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     format!("<{} as {}>::{}", self_ty_name, trait_name, method_name.name,),
                     Applicability::MachineApplicable,
                 );
-
-                lint
             },
         );
     }
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 4243bce377f..bbcc04af6f3 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -445,7 +445,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         scope_expr_id,
                         span,
                         "type annotations needed",
-                        |lint| lint,
+                        |_| {},
                     );
                 }
             } else {
@@ -1427,8 +1427,6 @@ impl<'tcx> Pick<'tcx> {
                         ));
                     }
                 }
-
-                lint
             },
         );
     }
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index be21fd5f0a6..56a420fab4f 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -1849,8 +1849,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         lint.note(format!(
             "the pattern is of type `{ty}` and the `non_exhaustive_omitted_patterns` attribute was found",
         ));
-
-        lint
     });
     }
 
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs
index 998ee339ae2..69d6fb8e2ea 100644
--- a/compiler/rustc_hir_typeck/src/upvar.rs
+++ b/compiler/rustc_hir_typeck/src/upvar.rs
@@ -912,8 +912,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             Applicability::HasPlaceholders
                         );
                     }
-
-                    lint
                 },
             );
         }
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 32eb67ba3a1..045ff38c056 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -2800,7 +2800,7 @@ impl<'tcx> LateLintPass<'tcx> for NamedAsmLabels {
                             NAMED_ASM_LABELS,
                             Some(target_spans),
                             fluent::lint_builtin_asm_labels,
-                            |lint| lint,
+                            |_| {},
                             BuiltinLintDiagnostics::NamedAsmLabel(
                                 "only local labels of the form `<number>:` should be used in inline asm"
                                     .to_string(),
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 0911fa70f97..c7a9d5e80ac 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -520,9 +520,6 @@ pub trait LintContext {
     /// Emit a lint at the appropriate level, with an optional associated span and an existing
     /// diagnostic.
     ///
-    /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed
-    /// explanation.
-    ///
     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
     #[rustc_lint_diagnostics]
     fn lookup_with_diagnostics(
@@ -530,9 +527,7 @@ pub trait LintContext {
         lint: &'static Lint,
         span: Option<impl Into<MultiSpan>>,
         msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
         diagnostic: BuiltinLintDiagnostics,
     ) {
         // We first generate a blank diagnostic.
@@ -986,8 +981,6 @@ pub trait LintContext {
     // set the span in their `decorate` function (preferably using set_span).
     /// Emit a lint at the appropriate level, with an optional associated span.
     ///
-    /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
-    ///
     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
     #[rustc_lint_diagnostics]
     fn lookup<S: Into<MultiSpan>>(
@@ -995,9 +988,7 @@ pub trait LintContext {
         lint: &'static Lint,
         span: Option<S>,
         msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
     );
 
     /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
@@ -1008,13 +999,13 @@ pub trait LintContext {
         span: S,
         decorator: impl for<'a> DecorateLint<'a, ()>,
     ) {
-        self.lookup(lint, Some(span), decorator.msg(), |diag| decorator.decorate_lint(diag));
+        self.lookup(lint, Some(span), decorator.msg(), |diag| {
+            decorator.decorate_lint(diag);
+        });
     }
 
     /// Emit a lint at the appropriate level, with an associated span.
     ///
-    /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
-    ///
     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
     #[rustc_lint_diagnostics]
     fn struct_span_lint<S: Into<MultiSpan>>(
@@ -1022,9 +1013,7 @@ pub trait LintContext {
         lint: &'static Lint,
         span: S,
         msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
     ) {
         self.lookup(lint, Some(span), msg, decorate);
     }
@@ -1033,23 +1022,19 @@ pub trait LintContext {
     /// generated by `#[derive(LintDiagnostic)]`).
     fn emit_lint(&self, lint: &'static Lint, decorator: impl for<'a> DecorateLint<'a, ()>) {
         self.lookup(lint, None as Option<Span>, decorator.msg(), |diag| {
-            decorator.decorate_lint(diag)
+            decorator.decorate_lint(diag);
         });
     }
 
     /// Emit a lint at the appropriate level, with no associated span.
     ///
-    /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
-    ///
     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
     #[rustc_lint_diagnostics]
     fn lint(
         &self,
         lint: &'static Lint,
         msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
     ) {
         self.lookup(lint, None as Option<Span>, msg, decorate);
     }
@@ -1113,9 +1098,7 @@ impl<'tcx> LintContext for LateContext<'tcx> {
         lint: &'static Lint,
         span: Option<S>,
         msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
     ) {
         let hir_id = self.last_node_with_lint_attrs;
 
@@ -1142,9 +1125,7 @@ impl LintContext for EarlyContext<'_> {
         lint: &'static Lint,
         span: Option<S>,
         msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
     ) {
         self.builder.struct_lint(lint, span.map(|s| s.into()), msg, decorate)
     }
diff --git a/compiler/rustc_lint/src/early.rs b/compiler/rustc_lint/src/early.rs
index 4c7f9eeff8c..b9add9e9f06 100644
--- a/compiler/rustc_lint/src/early.rs
+++ b/compiler/rustc_lint/src/early.rs
@@ -45,13 +45,7 @@ impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
     fn inlined_check_id(&mut self, id: ast::NodeId) {
         for early_lint in self.context.buffered.take(id) {
             let BufferedEarlyLint { span, msg, node_id: _, lint_id, diagnostic } = early_lint;
-            self.context.lookup_with_diagnostics(
-                lint_id.lint,
-                Some(span),
-                msg,
-                |lint| lint,
-                diagnostic,
-            );
+            self.context.lookup_with_diagnostics(lint_id.lint, Some(span), msg, |_| {}, diagnostic);
         }
     }
 
diff --git a/compiler/rustc_lint/src/levels.rs b/compiler/rustc_lint/src/levels.rs
index c1d4ed37627..8c8ff3fc650 100644
--- a/compiler/rustc_lint/src/levels.rs
+++ b/compiler/rustc_lint/src/levels.rs
@@ -1077,7 +1077,6 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
                             GateIssue::Language,
                             lint_from_cli,
                         );
-                        lint
                     },
                 );
                 return false;
@@ -1094,8 +1093,6 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
     /// Used to emit a lint-related diagnostic based on the current state of
     /// this lint context.
     ///
-    /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
-    ///
     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
     #[rustc_lint_diagnostics]
     #[track_caller]
@@ -1104,9 +1101,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
         lint: &'static Lint,
         span: Option<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
     ) {
         let (level, src) = self.lint_level(lint);
         struct_lint_level(self.sess, lint, level, src, span, msg, decorate)
@@ -1121,7 +1116,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
     ) {
         let (level, src) = self.lint_level(lint);
         struct_lint_level(self.sess, lint, level, src, Some(span), decorate.msg(), |lint| {
-            decorate.decorate_lint(lint)
+            decorate.decorate_lint(lint);
         });
     }
 
@@ -1129,7 +1124,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
     pub fn emit_lint(&self, lint: &'static Lint, decorate: impl for<'a> DecorateLint<'a, ()>) {
         let (level, src) = self.lint_level(lint);
         struct_lint_level(self.sess, lint, level, src, None, decorate.msg(), |lint| {
-            decorate.decorate_lint(lint)
+            decorate.decorate_lint(lint);
         });
     }
 }
diff --git a/compiler/rustc_lint/src/non_fmt_panic.rs b/compiler/rustc_lint/src/non_fmt_panic.rs
index f0e415492ae..9fcd70ba0b5 100644
--- a/compiler/rustc_lint/src/non_fmt_panic.rs
+++ b/compiler/rustc_lint/src/non_fmt_panic.rs
@@ -126,7 +126,7 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
         lint.note(fluent::lint_more_info_note);
         if !is_arg_inside_call(arg_span, span) {
             // No clue where this argument is coming from.
-            return lint;
+            return;
         }
         if arg_macro.is_some_and(|id| cx.tcx.is_diagnostic_item(sym::format_macro, id)) {
             // A case of `panic!(format!(..))`.
@@ -207,7 +207,6 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
                 }
             }
         }
-        lint
     });
 }
 
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index eada116f896..4c4f38d1ad8 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -253,29 +253,10 @@ pub fn explain_lint_level_source(
 /// - [`TyCtxt::struct_lint_node`]
 /// - `LintContext::lookup`
 ///
-/// ## `decorate` signature
+/// ## `decorate`
 ///
-/// The return value of `decorate` is ignored by this function. So what is the
-/// point of returning `&'b mut DiagnosticBuilder<'a, ()>`?
-///
-/// There are 2 reasons for this signature.
-///
-/// First of all, it prevents accidental use of `.emit()` -- it's clear that the
-/// builder will be later used and shouldn't be emitted right away (this is
-/// especially important because the old API expected you to call `.emit()` in
-/// the closure).
-///
-/// Second of all, it makes the most common case of adding just a single label
-/// /suggestion much nicer, since [`DiagnosticBuilder`] methods return
-/// `&mut DiagnosticBuilder`, you can just chain methods, without needed
-/// awkward `{ ...; }`:
-/// ```ignore pseudo-code
-/// struct_lint_level(
-///     ...,
-///     |lint| lint.span_label(sp, "lbl")
-///     //          ^^^^^^^^^^^^^^^^^^^^^ returns `&mut DiagnosticBuilder` by default
-/// )
-/// ```
+/// It is not intended to call `emit`/`cancel` on the `DiagnosticBuilder` passed
+/// in the `decorate` callback.
 #[track_caller]
 pub fn struct_lint_level(
     sess: &Session,
@@ -284,9 +265,7 @@ pub fn struct_lint_level(
     src: LintLevelSource,
     span: Option<MultiSpan>,
     msg: impl Into<DiagnosticMessage>,
-    decorate: impl for<'a, 'b> FnOnce(
-        &'b mut DiagnosticBuilder<'a, ()>,
-    ) -> &'b mut DiagnosticBuilder<'a, ()>,
+    decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
 ) {
     // Avoid codegen bloat from monomorphization by immediately doing dyn dispatch of `decorate` to
     // the "real" work.
@@ -298,12 +277,7 @@ pub fn struct_lint_level(
         src: LintLevelSource,
         span: Option<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
-        decorate: Box<
-            dyn '_
-                + for<'a, 'b> FnOnce(
-                    &'b mut DiagnosticBuilder<'a, ()>,
-                ) -> &'b mut DiagnosticBuilder<'a, ()>,
-        >,
+        decorate: Box<dyn '_ + for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>)>,
     ) {
         // Check for future incompatibility lints and issue a stronger warning.
         let future_incompatible = lint.future_incompatible;
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 564a1fad14d..0cba6d5b52a 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -223,7 +223,6 @@ fn late_report_deprecation(
             let kind = tcx.def_descr(def_id);
             deprecation_suggestion(diag, kind, suggestion, method_span);
         }
-        diag
     });
 }
 
@@ -587,7 +586,7 @@ impl<'tcx> TyCtxt<'tcx> {
         unmarked: impl FnOnce(Span, DefId),
     ) -> bool {
         let soft_handler = |lint, span, msg: String| {
-            self.struct_span_lint_hir(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, msg, |lint| lint)
+            self.struct_span_lint_hir(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, msg, |_| {})
         };
         let eval_result =
             self.eval_stability_allow_unstable(def_id, id, span, method_span, allow_unstable);
diff --git a/compiler/rustc_middle/src/mir/interpret/queries.rs b/compiler/rustc_middle/src/mir/interpret/queries.rs
index 34068a9da37..092b59deeff 100644
--- a/compiler/rustc_middle/src/mir/interpret/queries.rs
+++ b/compiler/rustc_middle/src/mir/interpret/queries.rs
@@ -113,7 +113,7 @@ impl<'tcx> TyCtxt<'tcx> {
                                 self.local_def_id_to_hir_id(local_def_id),
                                 self.def_span(ct.def),
                                 "cannot use constants which depend on generic parameters in types",
-                                |err| err,
+                                |_| {},
                             )
                         }
                     }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 5e61847a37a..6a6ed59fabf 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -2030,14 +2030,12 @@ impl<'tcx> TyCtxt<'tcx> {
         let msg = decorator.msg();
         let (level, src) = self.lint_level_at_node(lint, hir_id);
         struct_lint_level(self.sess, lint, level, src, Some(span.into()), msg, |diag| {
-            decorator.decorate_lint(diag)
+            decorator.decorate_lint(diag);
         })
     }
 
     /// Emit a lint at the appropriate level for a hir node, with an associated span.
     ///
-    /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
-    ///
     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
     #[rustc_lint_diagnostics]
     #[track_caller]
@@ -2047,9 +2045,7 @@ impl<'tcx> TyCtxt<'tcx> {
         hir_id: HirId,
         span: impl Into<MultiSpan>,
         msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
     ) {
         let (level, src) = self.lint_level_at_node(lint, hir_id);
         struct_lint_level(self.sess, lint, level, src, Some(span.into()), msg, decorate);
@@ -2064,13 +2060,13 @@ impl<'tcx> TyCtxt<'tcx> {
         id: HirId,
         decorator: impl for<'a> DecorateLint<'a, ()>,
     ) {
-        self.struct_lint_node(lint, id, decorator.msg(), |diag| decorator.decorate_lint(diag))
+        self.struct_lint_node(lint, id, decorator.msg(), |diag| {
+            decorator.decorate_lint(diag);
+        })
     }
 
     /// Emit a lint at the appropriate level for a hir node.
     ///
-    /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
-    ///
     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
     #[rustc_lint_diagnostics]
     #[track_caller]
@@ -2079,9 +2075,7 @@ impl<'tcx> TyCtxt<'tcx> {
         lint: &'static Lint,
         id: HirId,
         msg: impl Into<DiagnosticMessage>,
-        decorate: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        decorate: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
     ) {
         let (level, src) = self.lint_level_at_node(lint, id);
         struct_lint_level(self.sess, lint, level, src, None, msg, decorate);
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index 818d1436659..533fe32f70d 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -273,7 +273,6 @@ fn overlap<'tcx>(
                                     causing the impls to overlap",
                                 infcx.resolve_vars_if_possible(failing_obligation.predicate)
                             ));
-                            lint
                         },
                     );
                 }
diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index fbde7455145..e3f89b3f5f6 100644
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -194,7 +194,6 @@ fn lint_object_unsafe_trait(
                 // Only provide the help if its a local trait, otherwise it's not
                 violation.solution().add_to(err);
             }
-            err
         },
     );
 }
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index 39f5ff52eba..71a88f5f07c 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -450,7 +450,6 @@ fn report_conflicting_impls<'tcx>(
                 msg,
                 |err| {
                     decorate(tcx, &overlap, impl_span, err);
-                    err
                 },
             );
         }
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 8215926ee33..0150496990d 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -380,7 +380,9 @@ pub(crate) fn run_global_ctxt(
             crate::lint::MISSING_CRATE_LEVEL_DOCS,
             DocContext::as_local_hir_id(tcx, krate.module.item_id).unwrap(),
             "no documentation found for this crate's top-level module",
-            |lint| lint.help(help),
+            |lint| {
+                lint.help(help);
+            },
         );
     }
 
diff --git a/src/librustdoc/html/markdown.rs b/src/librustdoc/html/markdown.rs
index dbd78ea0dc9..6f667d18e35 100644
--- a/src/librustdoc/html/markdown.rs
+++ b/src/librustdoc/html/markdown.rs
@@ -835,7 +835,7 @@ impl<'tcx> ExtraInfo<'tcx> {
                 self.tcx.local_def_id_to_hir_id(def_id),
                 self.sp,
                 msg,
-                |l| l,
+                |_| {},
             );
         }
     }
@@ -843,9 +843,7 @@ impl<'tcx> ExtraInfo<'tcx> {
     fn error_invalid_codeblock_attr_with_help(
         &self,
         msg: impl Into<DiagnosticMessage>,
-        f: impl for<'a, 'b> FnOnce(
-            &'b mut DiagnosticBuilder<'a, ()>,
-        ) -> &'b mut DiagnosticBuilder<'a, ()>,
+        f: impl for<'a, 'b> FnOnce(&'b mut DiagnosticBuilder<'a, ()>),
     ) {
         if let Some(def_id) = self.def_id.as_local() {
             self.tcx.struct_span_lint_hir(
@@ -1296,7 +1294,7 @@ impl LangString {
                                     lint.help(format!(
                                         "there is an attribute with a similar name: `edition{}`",
                                         &x[4..],
-                                    ))
+                                    ));
                                 },
                             );
                         }
@@ -1350,7 +1348,7 @@ impl LangString {
                                         lint.help(format!(
                                             "there is an attribute with a similar name: `{flag}`"
                                         ))
-                                        .help(help)
+                                        .help(help);
                                     },
                                 );
                             }
diff --git a/src/librustdoc/passes/check_doc_test_visibility.rs b/src/librustdoc/passes/check_doc_test_visibility.rs
index 8d5b17f43cd..a931e8804d9 100644
--- a/src/librustdoc/passes/check_doc_test_visibility.rs
+++ b/src/librustdoc/passes/check_doc_test_visibility.rs
@@ -131,7 +131,7 @@ pub(crate) fn look_for_tests<'tcx>(cx: &DocContext<'tcx>, dox: &str, item: &Item
                 hir_id,
                 sp,
                 "missing code example in this documentation",
-                |lint| lint,
+                |_| {},
             );
         }
     } else if tests.found_tests > 0
@@ -142,7 +142,7 @@ pub(crate) fn look_for_tests<'tcx>(cx: &DocContext<'tcx>, dox: &str, item: &Item
             hir_id,
             item.attr_span(cx.tcx),
             "documentation test in private item",
-            |lint| lint,
+            |_| {},
         );
     }
 }
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 6b536e97c43..ee185ab9892 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -1755,8 +1755,6 @@ fn report_diagnostic(
         }
 
         decorate(lint, span, link_range);
-
-        lint
     });
 }
 
diff --git a/src/librustdoc/passes/lint/bare_urls.rs b/src/librustdoc/passes/lint/bare_urls.rs
index 0c5cfffe1be..bffa17da3b4 100644
--- a/src/librustdoc/passes/lint/bare_urls.rs
+++ b/src/librustdoc/passes/lint/bare_urls.rs
@@ -31,7 +31,7 @@ pub(super) fn visit_item(cx: &DocContext<'_>, item: &Item) {
                             "use an automatic link instead",
                             format!("<{url}>"),
                             Applicability::MachineApplicable,
-                        )
+                        );
                 });
             };
 
diff --git a/src/librustdoc/passes/lint/check_code_block_syntax.rs b/src/librustdoc/passes/lint/check_code_block_syntax.rs
index e9b9e36a530..b5583ae4520 100644
--- a/src/librustdoc/passes/lint/check_code_block_syntax.rs
+++ b/src/librustdoc/passes/lint/check_code_block_syntax.rs
@@ -131,8 +131,6 @@ fn check_rust_syntax(
         for message in buffer.messages.iter() {
             lint.note(message.clone());
         }
-
-        lint
     });
 }
 
diff --git a/src/librustdoc/passes/lint/html_tags.rs b/src/librustdoc/passes/lint/html_tags.rs
index 4a80c22ed08..90874c01102 100644
--- a/src/librustdoc/passes/lint/html_tags.rs
+++ b/src/librustdoc/passes/lint/html_tags.rs
@@ -89,7 +89,7 @@ pub(crate) fn visit_item(cx: &DocContext<'_>, item: &Item) {
                     if (generics_start > 0 && dox.as_bytes()[generics_start - 1] == b'<')
                         || (generics_end < dox.len() && dox.as_bytes()[generics_end] == b'>')
                     {
-                        return lint;
+                        return;
                     }
                     // multipart form is chosen here because ``Vec<i32>`` would be confusing.
                     lint.multipart_suggestion(
@@ -101,8 +101,6 @@ pub(crate) fn visit_item(cx: &DocContext<'_>, item: &Item) {
                         Applicability::MaybeIncorrect,
                     );
                 }
-
-                lint
             });
         };
 
diff --git a/src/librustdoc/passes/lint/redundant_explicit_links.rs b/src/librustdoc/passes/lint/redundant_explicit_links.rs
index 472781e7d22..4491d20b478 100644
--- a/src/librustdoc/passes/lint/redundant_explicit_links.rs
+++ b/src/librustdoc/passes/lint/redundant_explicit_links.rs
@@ -181,8 +181,6 @@ fn check_inline_or_reference_unknown_redundancy(
                 .span_label(display_span, "because label contains path that resolves to same destination")
                 .note("when a link's destination is not specified,\nthe label is used to resolve intra-doc links")
                 .span_suggestion_with_style(link_span, "remove explicit link target", format!("[{}]", link_data.display_link), Applicability::MaybeIncorrect, SuggestionStyle::ShowAlways);
-
-            lint
         });
     }
 
@@ -234,8 +232,6 @@ fn check_reference_redundancy(
                 .span_note(def_span, "referenced explicit link target defined here")
                 .note("when a link's destination is not specified,\nthe label is used to resolve intra-doc links")
                 .span_suggestion_with_style(link_span, "remove explicit link target", format!("[{}]", link_data.display_link), Applicability::MaybeIncorrect, SuggestionStyle::ShowAlways);
-
-            lint
         });
     }
 
diff --git a/src/librustdoc/passes/lint/unescaped_backticks.rs b/src/librustdoc/passes/lint/unescaped_backticks.rs
index 8b7fdd6ab1f..0893cd0b40b 100644
--- a/src/librustdoc/passes/lint/unescaped_backticks.rs
+++ b/src/librustdoc/passes/lint/unescaped_backticks.rs
@@ -111,8 +111,6 @@ pub(crate) fn visit_item(cx: &DocContext<'_>, item: &Item) {
                     }
 
                     suggest_insertion(cx, item, &dox, lint, backtick_index, '\\', "if you meant to use a literal backtick, escape it");
-
-                    lint
                 });
             }
             Event::Code(_) => {
diff --git a/src/tools/clippy/clippy_utils/src/diagnostics.rs b/src/tools/clippy/clippy_utils/src/diagnostics.rs
index fa56e5b0ba2..7562961538e 100644
--- a/src/tools/clippy/clippy_utils/src/diagnostics.rs
+++ b/src/tools/clippy/clippy_utils/src/diagnostics.rs
@@ -49,7 +49,6 @@ pub fn span_lint<T: LintContext>(cx: &T, lint: &'static Lint, sp: impl Into<Mult
     #[expect(clippy::disallowed_methods)]
     cx.struct_span_lint(lint, sp, msg.to_string(), |diag| {
         docs_link(diag, lint);
-        diag
     });
 }
 
@@ -90,7 +89,6 @@ pub fn span_lint_and_help<T: LintContext>(
             diag.help(help.to_string());
         }
         docs_link(diag, lint);
-        diag
     });
 }
 
@@ -134,7 +132,6 @@ pub fn span_lint_and_note<T: LintContext>(
             diag.note(note);
         }
         docs_link(diag, lint);
-        diag
     });
 }
 
@@ -152,7 +149,6 @@ where
     cx.struct_span_lint(lint, sp, msg.to_string(), |diag| {
         f(diag);
         docs_link(diag, lint);
-        diag
     });
 }
 
@@ -160,7 +156,6 @@ pub fn span_lint_hir(cx: &LateContext<'_>, lint: &'static Lint, hir_id: HirId, s
     #[expect(clippy::disallowed_methods)]
     cx.tcx.struct_span_lint_hir(lint, hir_id, sp, msg.to_string(), |diag| {
         docs_link(diag, lint);
-        diag
     });
 }
 
@@ -176,7 +171,6 @@ pub fn span_lint_hir_and_then(
     cx.tcx.struct_span_lint_hir(lint, hir_id, sp, msg.to_string(), |diag| {
         f(diag);
         docs_link(diag, lint);
-        diag
     });
 }