Port #[rustc_paren_sugar] to the new attribute system

Author: GrigorenkoPV

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -280,6 +280,9 @@ pub enum AttributeKind {
     /// Represents `#[optimize(size|speed)]`
     Optimize(OptimizeAttr, Span),
 
+    /// Represents `#[rustc_paren_sugar]`.
+    ParenSugar(Span),
+
     /// Represents `#[rustc_pass_by_value]` (used by the `rustc_pass_by_value` lint).
     PassByValue(Span),
 

compiler/rustc_attr_parsing/src/attributes/traits.rs

@@ -138,9 +138,19 @@ impl<S: Stage> NoArgsAttributeParser<S> for MarkerParser {
 pub(crate) struct FundamentalParser;
 impl<S: Stage> NoArgsAttributeParser<S> for FundamentalParser {
     const PATH: &[Symbol] = &[sym::fundamental];
-    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
 
     fn create(_: Span) -> AttributeKind {
         AttributeKind::Fundamental
     }
 }
+
+pub(crate) struct ParenSugarParser;
+impl<S: Stage> NoArgsAttributeParser<S> for ParenSugarParser {
+    const PATH: &[Symbol] = &[sym::rustc_paren_sugar];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+
+    fn create(span: Span) -> AttributeKind {
+        AttributeKind::ParenSugar(span)
+    }
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -29,8 +29,8 @@ use crate::attributes::stability::{
 };
 use crate::attributes::traits::{
     CoinductiveParser, ConstTraitParser, DenyExplicitImplParser, DoNotImplementViaObjectParser,
-    FundamentalParser, MarkerParser, SkipDuringMethodDispatchParser, SpecializationTraitParser,
-    TypeConstParser, UnsafeSpecializationMarkerParser,
+    FundamentalParser, MarkerParser, ParenSugarParser, SkipDuringMethodDispatchParser,
+    SpecializationTraitParser, TypeConstParser, UnsafeSpecializationMarkerParser,
 };
 use crate::attributes::transparency::TransparencyParser;
 use crate::attributes::{AttributeParser as _, Combine, Single, WithoutArgs};
@@ -137,6 +137,7 @@ attribute_parsers!(
         Single<WithoutArgs<MarkerParser>>,
         Single<WithoutArgs<MayDangleParser>>,
         Single<WithoutArgs<NoMangleParser>>,
+        Single<WithoutArgs<ParenSugarParser>>,
         Single<WithoutArgs<PassByValueParser>>,
         Single<WithoutArgs<PubTransparentParser>>,
         Single<WithoutArgs<SpecializationTraitParser>>,

compiler/rustc_hir_analysis/src/collect.rs

@@ -1142,7 +1142,7 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::TraitDef {
         hir::Constness::NotConst
     };
 
-    let paren_sugar = attrs.iter().any(|attr| attr.has_name(sym::rustc_paren_sugar));
+    let paren_sugar = find_attr!(attrs, AttributeKind::ParenSugar(_));
     if paren_sugar && !tcx.features().unboxed_closures() {
         tcx.dcx().emit_err(errors::ParenSugarAttribute { span: item.span });
     }

compiler/rustc_parse/src/validate_attr.rs

@@ -304,6 +304,7 @@ fn emit_malformed_attribute(
             | sym::rustc_unsafe_specialization_marker
             | sym::marker
             | sym::fundamental
+            | sym::rustc_paren_sugar
             | sym::type_const
             | sym::rustc_pass_by_value
             | sym::repr

compiler/rustc_passes/src/check_attr.rs

@@ -129,9 +129,10 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 }
                 &Attribute::Parsed(
                     AttributeKind::SpecializationTrait(attr_span)
-                    | AttributeKind::UnsafeSpecializationMarker(attr_span),
+                    | AttributeKind::UnsafeSpecializationMarker(attr_span)
+                    | AttributeKind::ParenSugar(attr_span),
                 ) => {
-                    // FIXME(specialization): more validation is needed
+                    // FIXME: more validation is needed
                     self.check_must_be_applied_to_trait(attr_span, span, target);
                 }
                 &Attribute::Parsed(AttributeKind::TypeConst(attr_span)) => {