[clang] [HLSL] Update type for `out` arguments only for dependent params types (PR #163832)

[Tex Riddell via cfe-commits]

================
@@ -765,10 +765,18 @@ static bool isRelevantAttr(Sema &S, const Decl *D, const Attr *A) {
 
 static void instantiateDependentHLSLParamModifierAttr(
     Sema &S, const MultiLevelTemplateArgumentList &TemplateArgs,
-    const HLSLParamModifierAttr *Attr, Decl *New) {
-  ParmVarDecl *P = cast<ParmVarDecl>(New);
-  P->addAttr(Attr->clone(S.getASTContext()));
-  P->setType(S.HLSL().getInoutParameterType(P->getType()));
+    const HLSLParamModifierAttr *Attr, const Decl *Old, Decl *New) {
+  ParmVarDecl *NewParm = cast<ParmVarDecl>(New);
+  NewParm->addAttr(Attr->clone(S.getASTContext()));
+
+  const Type *OldParmTy = cast<ParmVarDecl>(Old)->getType().getTypePtr();
+  if (OldParmTy->isDependentType())
+    NewParm->setType(S.HLSL().getInoutParameterType(NewParm->getType()));
----------------
tex3d wrote:

Although I'm not as familiar with the code here as some others, from the context, I find it unexpected that a function called during a particular attribute instantiation might change the type of the `NewParm` Decl passed in.

Could there be a more appropriate place to update the type?

https://github.com/llvm/llvm-project/pull/163832