fix: lint against lint functions

fix: lint against the functions `LintContext::{lookup_with_diagnostics,lookup,struct_span_lint,lint}`, `TyCtxt::struct_lint_node`, `LintLevelsBuilder::struct_lint`.

compiler/rustc_lint/src/context.rs

@@ -579,6 +579,7 @@ pub trait LintContext: Sized {
     /// 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(
         &self,
         lint: &'static Lint,
@@ -882,6 +883,7 @@ pub trait LintContext: Sized {
     /// 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>>(
         &self,
         lint: &'static Lint,
@@ -908,6 +910,7 @@ pub trait LintContext: Sized {
     /// 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>>(
         &self,
         lint: &'static Lint,
@@ -933,6 +936,7 @@ pub trait LintContext: Sized {
     /// 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,

compiler/rustc_lint/src/levels.rs

@@ -1073,6 +1073,7 @@ impl<'s, P: LintLevelsProvider> LintLevelsBuilder<'s, P> {
     /// 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]
     pub(crate) fn struct_lint(
         &self,
         lint: &'static Lint,

compiler/rustc_lint/src/lib.rs

@@ -36,6 +36,7 @@
 #![feature(let_chains)]
 #![feature(min_specialization)]
 #![feature(never_type)]
+#![feature(rustc_attrs)]
 #![recursion_limit = "256"]
 
 #[macro_use]

compiler/rustc_middle/src/ty/context.rs

@@ -2856,6 +2856,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// 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]
     pub fn struct_lint_node(
         self,
         lint: &'static Lint,