Port #[rustc_paren_sugar] to the new attribute system

Author: GrigorenkoPV

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -325,6 +325,9 @@ 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_data_structures/src/encode_cross_crate.rs

@@ -49,6 +49,7 @@ impl AttributeKind {
             NoMangle(..) => No,
             NonExhaustive(..) => Yes,
             Optimize(..) => No,
+            ParenSugar(..) => No,
             PassByValue(..) => Yes,
             Path(..) => No,
             PubTransparent(..) => Yes,

compiler/rustc_attr_parsing/src/attributes/traits.rs

@@ -117,3 +117,10 @@ impl<S: Stage> NoArgsAttributeParser<S> for FundamentalParser {
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
     const CREATE: fn(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;
+    const CREATE: fn(Span) -> AttributeKind = AttributeKind::ParenSugar;
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -45,8 +45,8 @@ use crate::attributes::stability::{
 use crate::attributes::test_attrs::IgnoreParser;
 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};
@@ -168,6 +168,7 @@ attribute_parsers!(
         Single<WithoutArgs<NoImplicitPreludeParser>>,
         Single<WithoutArgs<NoMangleParser>>,
         Single<WithoutArgs<NonExhaustiveParser>>,
+        Single<WithoutArgs<ParenSugarParser>>,
         Single<WithoutArgs<PassByValueParser>>,
         Single<WithoutArgs<PubTransparentParser>>,
         Single<WithoutArgs<SpecializationTraitParser>>,

compiler/rustc_hir_analysis/src/collect.rs

@@ -860,7 +860,7 @@ 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

@@ -291,6 +291,7 @@ pub fn check_builtin_meta_item(
                 | sym::rustc_unsafe_specialization_marker
                 | sym::marker
                 | sym::fundamental
+                | sym::rustc_paren_sugar
                 | sym::type_const
                 | sym::repr
                 | sym::align

compiler/rustc_passes/src/check_attr.rs

@@ -131,9 +131,10 @@ 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)) => {