Port #[rustc_coinductive] to the new attribute system

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -211,6 +211,9 @@ pub enum AttributeKind {
         span: Span,
     },
 
+    /// Represents `#[rustc_coinductive]`.
+    Coinductive(Span),
+
     /// Represents `#[cold]`.
     Cold(Span),
 

compiler/rustc_attr_data_structures/src/encode_cross_crate.rs

@@ -18,6 +18,7 @@ impl AttributeKind {
             AllowInternalUnstable(..) => Yes,
             AsPtr(..) => Yes,
             BodyStability { .. } => No,
+            Coinductive(..) => No,
             Cold(..) => No,
             Confusables { .. } => Yes,
             ConstContinue(..) => No,

compiler/rustc_attr_parsing/src/attributes/traits.rs

@@ -75,3 +75,10 @@ impl<S: Stage> NoArgsAttributeParser<S> for DoNotImplementViaObjectParser {
     const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
     const CREATE: fn(Span) -> AttributeKind = AttributeKind::DoNotImplementViaObject;
 }
+
+pub(crate) struct CoinductiveParser;
+impl<S: Stage> NoArgsAttributeParser<S> for CoinductiveParser {
+    const PATH: &[Symbol] = &[sym::rustc_coinductive];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const CREATE: fn(Span) -> AttributeKind = AttributeKind::Coinductive;
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -44,7 +44,7 @@ use crate::attributes::stability::{
 };
 use crate::attributes::test_attrs::IgnoreParser;
 use crate::attributes::traits::{
-    ConstTraitParser, DenyExplicitImplParser, DoNotImplementViaObjectParser,
+    CoinductiveParser, ConstTraitParser, DenyExplicitImplParser, DoNotImplementViaObjectParser,
     SkipDuringMethodDispatchParser,
 };
 use crate::attributes::transparency::TransparencyParser;
@@ -150,6 +150,7 @@ attribute_parsers!(
         Single<SkipDuringMethodDispatchParser>,
         Single<TransparencyParser>,
         Single<WithoutArgs<AsPtrParser>>,
+        Single<WithoutArgs<CoinductiveParser>>,
         Single<WithoutArgs<ColdParser>>,
         Single<WithoutArgs<ConstContinueParser>>,
         Single<WithoutArgs<ConstStabilityIndirectParser>>,

compiler/rustc_hir_analysis/src/collect.rs

@@ -868,7 +868,7 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::TraitDef {
     // Only regular traits can be marker.
     let is_marker = !is_alias && attrs.iter().any(|attr| attr.has_name(sym::marker));
 
-    let rustc_coinductive = attrs.iter().any(|attr| attr.has_name(sym::rustc_coinductive));
+    let rustc_coinductive = find_attr!(attrs, AttributeKind::Coinductive(_));
     let is_fundamental = attrs.iter().any(|attr| attr.has_name(sym::fundamental));
 
     let [skip_array_during_method_dispatch, skip_boxed_slice_during_method_dispatch] = find_attr!(

compiler/rustc_parse/src/validate_attr.rs

@@ -285,6 +285,7 @@ pub fn check_builtin_meta_item(
                 | sym::rustc_pass_by_value
                 | sym::rustc_deny_explicit_impl
                 | sym::rustc_do_not_implement_via_object
+                | sym::rustc_coinductive
                 | sym::const_trait
                 | sym::repr
                 | sym::align

compiler/rustc_passes/src/check_attr.rs

@@ -122,6 +122,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             match attr {
                 Attribute::Parsed(
                     AttributeKind::SkipDuringMethodDispatch { span: attr_span, .. }
+                    | AttributeKind::Coinductive(attr_span)
                     | AttributeKind::ConstTrait(attr_span)
                     | AttributeKind::DenyExplicitImpl(attr_span)
                     | AttributeKind::DoNotImplementViaObject(attr_span),
@@ -299,9 +300,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         | [sym::rustc_dirty, ..]
                         | [sym::rustc_if_this_changed, ..]
                         | [sym::rustc_then_this_would_need, ..] => self.check_rustc_dirty_clean(attr),
-                        [sym::rustc_coinductive, ..]
-                        | [sym::rustc_must_implement_one_of, ..]
-                        => self.check_must_be_applied_to_trait(attr.span(), span, target),
+                        [sym::rustc_must_implement_one_of, ..] => self.check_must_be_applied_to_trait(attr.span(), span, target),
                         [sym::collapse_debuginfo, ..] => self.check_collapse_debuginfo(attr, span, target),
                         [sym::must_not_suspend, ..] => self.check_must_not_suspend(attr, span, target),
                         [sym::rustc_allow_incoherent_impl, ..] => {