From a51a793472fc6ba16247ddc06e366f7993d8ae93 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jana=20D=C3=B6nszelmann?= <jana@donsz.nl>
Date: Tue, 14 Oct 2025 17:27:38 +0200
Subject: [PATCH] only check duplicates on old/unparsed attributes

---
 compiler/rustc_passes/src/check_attr.rs | 33 ++++++++++++++++---------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index cba6243fa1098..5f0d7cdb59ef0 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -393,8 +393,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 }
             }
 
-            let builtin = attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name));
-
             if hir_id != CRATE_HIR_ID {
                 match attr {
                     Attribute::Parsed(_) => { /* Already validated. */ }
@@ -440,8 +438,18 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 }
             }
 
-            if let Some(BuiltinAttribute { duplicates, .. }) = builtin {
-                check_duplicates(self.tcx, attr, hir_id, *duplicates, &mut seen);
+            if let Attribute::Unparsed(unparsed_attr) = attr
+                && let Some(BuiltinAttribute { duplicates, .. }) =
+                    attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name))
+            {
+                check_duplicates(
+                    self.tcx,
+                    unparsed_attr.span,
+                    attr,
+                    hir_id,
+                    *duplicates,
+                    &mut seen,
+                );
             }
 
             self.check_unused_attribute(hir_id, attr, style)
@@ -2481,6 +2489,7 @@ pub(crate) fn provide(providers: &mut Providers) {
 // FIXME(jdonszelmann): remove, check during parsing
 fn check_duplicates(
     tcx: TyCtxt<'_>,
+    attr_span: Span,
     attr: &Attribute,
     hir_id: HirId,
     duplicates: AttributeDuplicates,
@@ -2497,10 +2506,10 @@ fn check_duplicates(
             match seen.entry(attr_name) {
                 Entry::Occupied(mut entry) => {
                     let (this, other) = if matches!(duplicates, FutureWarnPreceding) {
-                        let to_remove = entry.insert(attr.span());
-                        (to_remove, attr.span())
+                        let to_remove = entry.insert(attr_span);
+                        (to_remove, attr_span)
                     } else {
-                        (attr.span(), *entry.get())
+                        (attr_span, *entry.get())
                     };
                     tcx.emit_node_span_lint(
                         UNUSED_ATTRIBUTES,
@@ -2517,22 +2526,22 @@ fn check_duplicates(
                     );
                 }
                 Entry::Vacant(entry) => {
-                    entry.insert(attr.span());
+                    entry.insert(attr_span);
                 }
             }
         }
         ErrorFollowing | ErrorPreceding => match seen.entry(attr_name) {
             Entry::Occupied(mut entry) => {
                 let (this, other) = if matches!(duplicates, ErrorPreceding) {
-                    let to_remove = entry.insert(attr.span());
-                    (to_remove, attr.span())
+                    let to_remove = entry.insert(attr_span);
+                    (to_remove, attr_span)
                 } else {
-                    (attr.span(), *entry.get())
+                    (attr_span, *entry.get())
                 };
                 tcx.dcx().emit_err(errors::UnusedMultiple { this, other, name: attr_name });
             }
             Entry::Vacant(entry) => {
-                entry.insert(attr.span());
+                entry.insert(attr_span);
             }
         },
     }