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

[Erich Keane via cfe-commits]

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@@ -1197,25 +1197,17 @@ 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(
+    auto NewBindingPack = *llvm::find_if(
         Bindings, [](BindingDecl *D) -> bool { return D->isParameterPack(); });
-    auto *NewResolvedPack =
-        cast<ResolvedUnexpandedPackExpr>((*BPack)->getBinding());
-    auto OldExprs = OldResolvedPack->getExprs();
-    auto NewExprs = NewResolvedPack->getExprs();
-    assert(OldExprs.size() == NewExprs.size());
-    for (unsigned I = 0; I < OldResolvedPack->getNumExprs(); I++) {
-      DeclRefExpr *OldDRE = cast<DeclRefExpr>(OldExprs[I]);
-      BindingDecl *OldNestedBD = cast<BindingDecl>(OldDRE->getDecl());
-      DeclRefExpr *NewDRE = cast<DeclRefExpr>(NewExprs[I]);
-      BindingDecl *NewNestedBD = cast<BindingDecl>(NewDRE->getDecl());
-      SemaRef.CurrentInstantiationScope->InstantiatedLocal(OldNestedBD,
-                                                           NewNestedBD);
-    }
+    auto OldDecls = OldBindingPack->getBindingPackDecls();
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erichkeane wrote:

We shouldn't be using 'auto' on either of these.  I realize they already were, but please change them anyway.,

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