[clang] [Clang][P1061] Add stuctured binding packs (PR #121417)

[Jason Rice via cfe-commits]

================
@@ -50,17 +50,29 @@ class CollectUnexpandedParameterPacksVisitor
         auto *FTD = FD ? FD->getDescribedFunctionTemplate() : nullptr;
         if (FTD && FTD->getTemplateParameters()->getDepth() >= DepthLimit)
           return;
-      } else if (getDepthAndIndex(ND).first >= DepthLimit)
+      } else if (auto *BD = dyn_cast<BindingDecl>(ND)) {
+        Expr *E = BD->getBinding();
+        if (auto *RP = dyn_cast_if_present<ResolvedUnexpandedPackExpr>(E)) {
+          addUnexpanded(RP);
+          return;
+        }
----------------
ricejasonf wrote:

I changed it to `cast_if_present` since a dependent decomposition leaves the binding expr as nullptr.

https://github.com/llvm/llvm-project/pull/121417