Avoid layering violation

Author: zyn0217

clang/include/clang/AST/ExprCXX.h

@@ -4326,6 +4326,8 @@ class SizeOfPackExpr final
   /// Retrieve the parameter pack.
   NamedDecl *getPack() const { return Pack; }
 
+  void setPack(NamedDecl *NewPack) { Pack = NewPack; }
+
   /// Retrieve the length of the parameter pack.
   ///
   /// This routine may only be invoked when the expression is not

clang/lib/Sema/SemaTemplateInstantiate.cpp

@@ -1731,21 +1731,21 @@ namespace {
       return inherited::TransformLambdaBody(E, Body);
     }
 
-    ExprResult RebuildSizeOfPackExpr(SourceLocation OperatorLoc,
-                                     NamedDecl *Pack, SourceLocation PackLoc,
-                                     SourceLocation RParenLoc,
-                                     std::optional<unsigned> Length,
-                                     ArrayRef<TemplateArgument> PartialArgs) {
-      Decl *NewPack = Pack;
+    ExprResult TransformSizeOfPackExpr(SizeOfPackExpr *E) {
+      ExprResult Transformed = inherited::TransformSizeOfPackExpr(E);
+      if (!Transformed.isUsable())
+        return Transformed;
+      auto *TransformedExpr = cast<SizeOfPackExpr>(Transformed.get());
       if (SemaRef.CodeSynthesisContexts.back().Kind ==
-          Sema::CodeSynthesisContext::ConstraintNormalization) {
-        NewPack = TransformDecl(PackLoc, Pack);
+              Sema::CodeSynthesisContext::ConstraintNormalization &&
+          TransformedExpr->getPack() == E->getPack()) {
+        Decl *NewPack =
+            TransformDecl(E->getPackLoc(), TransformedExpr->getPack());
         if (!NewPack)
           return ExprError();
+        TransformedExpr->setPack(cast<NamedDecl>(NewPack));
       }
-      return inherited::RebuildSizeOfPackExpr(OperatorLoc,
-                                              cast<NamedDecl>(NewPack), PackLoc,
-                                              RParenLoc, Length, PartialArgs);
+      return TransformedExpr;
     }
 
     ExprResult TransformRequiresExpr(RequiresExpr *E) {