[clang] [Sema] Propagate preferred_name attribute to existing specializations (PR #186741)

[Younan Zhang via cfe-commits]

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@@ -1222,7 +1221,19 @@ static void handlePreferredName(Sema &S, Decl *D, const ParsedAttr &AL) {
     }
 
     if (Template && declaresSameEntity(Template, CTD)) {
-      D->addAttr(::new (S.Context) PreferredNameAttr(S.Context, AL, TSI));
+      auto *PNA = ::new (S.Context) PreferredNameAttr(S.Context, AL, TSI);
+      D->addAttr(PNA);
+
+      for (auto *Spec : CTD->specializations()) {
+        const TypeDecl *TD = static_cast<const TypeDecl *>(Spec);
+        if (S.Context.hasSameType(S.Context.getTypeDeclType(TD),
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zyn0217 wrote:

What makes it necessary to check the same type here?

https://github.com/llvm/llvm-project/pull/186741