New `#[rustc_pub_transparent]` attribute

2 files changed, 22 insertions, 0 deletions

diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index c93fb5c23b1..9ca4bb09b3e 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -245,6 +245,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     self.check_coroutine(attr, target);
                 }
                 [sym::linkage, ..] => self.check_linkage(attr, span, target),
+                [sym::rustc_pub_transparent, ..] => self.check_rustc_pub_transparent( attr.span, span, attrs),
                 [
                     // ok
                     sym::allow
@@ -2381,6 +2382,18 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             }
         }
     }
+
+    fn check_rustc_pub_transparent(&self, attr_span: Span, span: Span, attrs: &[Attribute]) {
+        if !attrs
+            .iter()
+            .filter(|attr| attr.has_name(sym::repr))
+            .filter_map(|attr| attr.meta_item_list())
+            .flatten()
+            .any(|nmi| nmi.has_name(sym::transparent))
+        {
+            self.dcx().emit_err(errors::RustcPubTransparent { span, attr_span });
+        }
+    }
 }
 
 impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> {
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 1190e60f41f..f6a57b7d098 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -623,6 +623,15 @@ pub struct RustcStdInternalSymbol {
 }
 
 #[derive(Diagnostic)]
+#[diag(passes_rustc_pub_transparent)]
+pub struct RustcPubTransparent {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(passes_link_ordinal)]
 pub struct LinkOrdinal {
     #[primary_span]