errors: introduce `DecorateLint`

Add a new trait to be generated by diagnostic derives which uses a
`LintDiagnosticBuilder`.

Signed-off-by: David Wood <david.wood@huawei.com>

2 files changed, 22 insertions, 2 deletions

diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 1e1c423982b..83328093e9f 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -22,7 +22,9 @@ use rustc_ast::util::unicode::TEXT_FLOW_CONTROL_CHARS;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync;
 use rustc_errors::{add_elided_lifetime_in_path_suggestion, struct_span_err};
-use rustc_errors::{Applicability, LintDiagnosticBuilder, MultiSpan, SuggestionStyle};
+use rustc_errors::{
+    Applicability, DecorateLint, LintDiagnosticBuilder, MultiSpan, SuggestionStyle,
+};
 use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::{CrateNum, DefId};
@@ -870,6 +872,17 @@ pub trait LintContext: Sized {
         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
     );
 
+    /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
+    /// typically generated by `#[derive(LintDiagnostic)]`).
+    fn emit_spanned_lint<S: Into<MultiSpan>>(
+        &self,
+        lint: &'static Lint,
+        span: S,
+        decorator: impl for<'a> DecorateLint<'a, ()>,
+    ) {
+        self.lookup(lint, Some(span), |diag| decorator.decorate_lint(diag));
+    }
+
     fn struct_span_lint<S: Into<MultiSpan>>(
         &self,
         lint: &'static Lint,
@@ -878,6 +891,13 @@ pub trait LintContext: Sized {
     ) {
         self.lookup(lint, Some(span), decorate);
     }
+
+    /// Emit a lint from a lint struct (some type that implements `DecorateLint`, typically
+    /// generated by `#[derive(LintDiagnostic)]`).
+    fn emit_lint(&self, lint: &'static Lint, decorator: impl for<'a> DecorateLint<'a, ()>) {
+        self.lookup(lint, None as Option<Span>, |diag| decorator.decorate_lint(diag));
+    }
+
     /// Emit a lint at the appropriate level, with no associated span.
     fn lint(
         &self,
diff --git a/compiler/rustc_lint/src/internal.rs b/compiler/rustc_lint/src/internal.rs
index 5bcf9390c07..738f475983e 100644
--- a/compiler/rustc_lint/src/internal.rs
+++ b/compiler/rustc_lint/src/internal.rs
@@ -414,7 +414,7 @@ impl LateLintPass<'_> for Diagnostics {
                 let Impl { of_trait: Some(of_trait), .. } = impl_ &&
                 let Some(def_id) = of_trait.trait_def_id() &&
                 let Some(name) = cx.tcx.get_diagnostic_name(def_id) &&
-                matches!(name, sym::SessionDiagnostic | sym::AddSubdiagnostic)
+                matches!(name, sym::SessionDiagnostic | sym::AddSubdiagnostic | sym::DecorateLint)
             {
                 found_impl = true;
                 break;