macros: LintDiagnostic derive

Cargo.lock

@@ -4009,6 +4009,7 @@ dependencies = [
  "rustc_hir",
  "rustc_index",
  "rustc_infer",
+ "rustc_macros",
  "rustc_middle",
  "rustc_parse_format",
  "rustc_session",

compiler/rustc_errors/src/diagnostic.rs

@@ -1,7 +1,7 @@
 use crate::snippet::Style;
 use crate::{
-    CodeSuggestion, DiagnosticMessage, Level, MultiSpan, SubdiagnosticMessage, Substitution,
-    SubstitutionPart, SuggestionStyle,
+    CodeSuggestion, DiagnosticMessage, EmissionGuarantee, Level, LintDiagnosticBuilder, MultiSpan,
+    SubdiagnosticMessage, Substitution, SubstitutionPart, SuggestionStyle,
 };
 use rustc_data_structures::stable_map::FxHashMap;
 use rustc_error_messages::FluentValue;
@@ -168,6 +168,14 @@ pub trait AddSubdiagnostic {
     fn add_to_diagnostic(self, diag: &mut Diagnostic);
 }
 
+/// Trait implemented by lint types. This should not be implemented manually. Instead, use
+/// `#[derive(LintDiagnostic)]` -- see [rustc_macros::LintDiagnostic].
+#[rustc_diagnostic_item = "DecorateLint"]
+pub trait DecorateLint<'a, G: EmissionGuarantee> {
+    /// Decorate and emit a lint.
+    fn decorate_lint(self, diag: LintDiagnosticBuilder<'a, G>);
+}
+
 #[must_use]
 #[derive(Clone, Debug, Encodable, Decodable)]
 pub struct Diagnostic {

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -589,3 +589,26 @@ macro_rules! struct_span_err {
 macro_rules! error_code {
     ($code:ident) => {{ $crate::DiagnosticId::Error(stringify!($code).to_owned()) }};
 }
+
+/// Wrapper around a `DiagnosticBuilder` for creating lints.
+pub struct LintDiagnosticBuilder<'a, G: EmissionGuarantee>(DiagnosticBuilder<'a, G>);
+
+impl<'a, G: EmissionGuarantee> LintDiagnosticBuilder<'a, G> {
+    /// Return the inner `DiagnosticBuilder`, first setting the primary message to `msg`.
+    pub fn build(mut self, msg: impl Into<DiagnosticMessage>) -> DiagnosticBuilder<'a, G> {
+        self.0.set_primary_message(msg);
+        self.0.set_is_lint();
+        self.0
+    }
+
+    /// Create a `LintDiagnosticBuilder` from some existing `DiagnosticBuilder`.
+    pub fn new(err: DiagnosticBuilder<'a, G>) -> LintDiagnosticBuilder<'a, G> {
+        LintDiagnosticBuilder(err)
+    }
+}
+
+impl<'a> LintDiagnosticBuilder<'a, ErrorGuaranteed> {
+    pub fn forget_guarantee(self) -> LintDiagnosticBuilder<'a, ()> {
+        LintDiagnosticBuilder(self.0.forget_guarantee())
+    }
+}

compiler/rustc_errors/src/lib.rs

@@ -370,10 +370,10 @@ impl fmt::Display for ExplicitBug {
 impl error::Error for ExplicitBug {}
 
 pub use diagnostic::{
-    AddSubdiagnostic, Diagnostic, DiagnosticArg, DiagnosticArgValue, DiagnosticId,
+    AddSubdiagnostic, DecorateLint, Diagnostic, DiagnosticArg, DiagnosticArgValue, DiagnosticId,
     DiagnosticStyledString, IntoDiagnosticArg, SubDiagnostic,
 };
-pub use diagnostic_builder::{DiagnosticBuilder, EmissionGuarantee};
+pub use diagnostic_builder::{DiagnosticBuilder, EmissionGuarantee, LintDiagnosticBuilder};
 use std::backtrace::Backtrace;
 
 /// A handler deals with errors and other compiler output.

compiler/rustc_lint/Cargo.toml

@@ -22,3 +22,4 @@ rustc_trait_selection = { path = "../rustc_trait_selection" }
 rustc_parse_format = { path = "../rustc_parse_format" }
 rustc_infer = { path = "../rustc_infer" }
 rustc_type_ir = { path = "../rustc_type_ir" }
+rustc_macros = { path = "../rustc_macros" }

compiler/rustc_lint/src/builtin.rs

@@ -32,15 +32,16 @@ use rustc_ast_pretty::pprust::{self, expr_to_string};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::{
-    fluent, Applicability, Diagnostic, DiagnosticMessage, DiagnosticStyledString, MultiSpan,
+    fluent, Applicability, Diagnostic, DiagnosticMessage, DiagnosticStyledString,
+    LintDiagnosticBuilder, MultiSpan,
 };
 use rustc_feature::{deprecated_attributes, AttributeGate, BuiltinAttribute, GateIssue, Stability};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId, LocalDefIdSet, CRATE_DEF_ID};
 use rustc_hir::{ForeignItemKind, GenericParamKind, HirId, PatKind, PredicateOrigin};
 use rustc_index::vec::Idx;
-use rustc_middle::lint::{in_external_macro, LintDiagnosticBuilder};
+use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::subst::GenericArgKind;

compiler/rustc_lint/src/context.rs

@@ -22,12 +22,13 @@ 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, 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};
 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
-use rustc_middle::lint::LintDiagnosticBuilder;
 use rustc_middle::middle::privacy::AccessLevels;
 use rustc_middle::middle::stability;
 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
@@ -871,6 +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,
@@ -879,6 +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,

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;

compiler/rustc_lint/src/levels.rs

@@ -3,13 +3,13 @@ use crate::late::unerased_lint_store;
 use rustc_ast as ast;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_errors::{struct_span_err, Applicability, Diagnostic, MultiSpan};
+use rustc_errors::{struct_span_err, Applicability, Diagnostic, LintDiagnosticBuilder, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::{intravisit, HirId};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::lint::{
-    struct_lint_level, LevelAndSource, LintDiagnosticBuilder, LintExpectation, LintLevelMap,
-    LintLevelSets, LintLevelSource, LintSet, LintStackIndex, COMMAND_LINE,
+    struct_lint_level, LevelAndSource, LintExpectation, LintLevelMap, LintLevelSets,
+    LintLevelSource, LintSet, LintStackIndex, COMMAND_LINE,
 };
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{RegisteredTools, TyCtxt};

compiler/rustc_lint/src/types.rs

@@ -5,6 +5,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{fluent, Applicability, DiagnosticMessage};
 use rustc_hir as hir;
 use rustc_hir::{is_range_literal, Expr, ExprKind, Node};
+use rustc_macros::LintDiagnostic;
 use rustc_middle::ty::layout::{IntegerExt, LayoutOf, SizeSkeleton};
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable};
@@ -1553,13 +1554,20 @@ impl InvalidAtomicOrdering {
         let Some(fail_ordering) = Self::match_ordering(cx, fail_order_arg) else { return };
 
         if matches!(fail_ordering, sym::Release | sym::AcqRel) {
-            cx.struct_span_lint(INVALID_ATOMIC_ORDERING, fail_order_arg.span, |diag| {
-                diag.build(fluent::lint::atomic_ordering_invalid)
-                    .set_arg("method", method)
-                    .span_label(fail_order_arg.span, fluent::lint::label)
-                    .help(fluent::lint::help)
-                    .emit();
-            });
+            #[derive(LintDiagnostic)]
+            #[lint(lint::atomic_ordering_invalid)]
+            #[help]
+            struct InvalidAtomicOrderingDiag {
+                method: Symbol,
+                #[label]
+                fail_order_arg_span: Span,
+            }
+
+            cx.emit_spanned_lint(
+                INVALID_ATOMIC_ORDERING,
+                fail_order_arg.span,
+                InvalidAtomicOrderingDiag { method, fail_order_arg_span: fail_order_arg.span },
+            );
         }
 
         let Some(success_ordering) = Self::match_ordering(cx, success_order_arg) else { return };