Port #[rustc_pub_transparent] to the new attribute system

compiler/rustc_attr_parsing/src/attributes/lint_helpers.rs

@@ -19,3 +19,16 @@ impl<S: Stage> SingleAttributeParser<S> for AsPtrParser {
         Some(AttributeKind::AsPtr(cx.attr_span))
     }
 }
+
+pub(crate) struct PubTransparentParser;
+impl<S: Stage> SingleAttributeParser<S> for PubTransparentParser {
+    const PATH: &[Symbol] = &[sym::rustc_pub_transparent];
+    const ATTRIBUTE_ORDER: AttributeOrder = AttributeOrder::KeepFirst;
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const TEMPLATE: AttributeTemplate = template!(Word);
+
+    fn convert(cx: &mut AcceptContext<'_, '_, S>, _args: &ArgParser<'_>) -> Option<AttributeKind> {
+        // FIXME: check that there's no args (this is currently checked elsewhere)
+        Some(AttributeKind::PubTransparent(cx.attr_span))
+    }
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -19,7 +19,7 @@ use crate::attributes::codegen_attrs::{ColdParser, OptimizeParser};
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
-use crate::attributes::lint_helpers::AsPtrParser;
+use crate::attributes::lint_helpers::{AsPtrParser, PubTransparentParser};
 use crate::attributes::repr::{AlignParser, ReprParser};
 use crate::attributes::semantics::MayDangleParser;
 use crate::attributes::stability::{
@@ -113,6 +113,7 @@ attribute_parsers!(
         Single<InlineParser>,
         Single<MayDangleParser>,
         Single<OptimizeParser>,
+        Single<PubTransparentParser>,
         Single<RustcForceInlineParser>,
         Single<TransparencyParser>,
         // tidy-alphabetical-end