[clang] [Clang][P1061] Consolidate ResolvedUnpexandedPackExpr into FunctionParmPackExpr (PR #125394)

[Younan Zhang via cfe-commits]

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@@ -1197,25 +1197,19 @@ Decl *TemplateDeclInstantiator::VisitDecompositionDecl(DecompositionDecl *D) {
     for (auto *NewBD : NewBindings)
       NewBD->setInvalidDecl();
 
-  if (OldResolvedPack) {
-    // Mark the holding vars (if any) in the pack as instantiated since
-    // they are created implicitly.
+  if (OldBindingPack) {
+    // Mark the bindings in the pack as instantiated.
     auto Bindings = NewDD->bindings();
-    auto BPack = llvm::find_if(
+    BindingDecl *NewBindingPack = *llvm::find_if(
         Bindings, [](BindingDecl *D) -> bool { return D->isParameterPack(); });
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zyn0217 wrote:

For sanity (we have lost the assertion of `cast`ing a non-null pointer), we'd better add an non-null assertion here

https://github.com/llvm/llvm-project/pull/125394