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

[via cfe-commits]

================
@@ -3395,26 +3395,37 @@ VarDecl *ValueDecl::getPotentiallyDecomposedVarDecl() {
   if (auto *Var = llvm::dyn_cast<VarDecl>(this))
     return Var;
   if (auto *BD = llvm::dyn_cast<BindingDecl>(this))
-    return llvm::dyn_cast<VarDecl>(BD->getDecomposedDecl());
+    return llvm::dyn_cast_or_null<VarDecl>(BD->getDecomposedDecl());
----------------
cor3ntin wrote:

```suggestion
    return llvm::dyn_cast_if_present<VarDecl>(BD->getDecomposedDecl());
```

Same change here and everywhere

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