[CSGen] Detect nested out-of-scope variables in recursive declarations

Follow-up to https://github.com/apple/swift/pull/63505

Since, when the type is not stated, a variable assumes the
type of its initializer that enables out-of-scope variables
to be nested inside of some other concrete type i.e. Optional.

Resolves: https://github.com/apple/swift/issues/63455

lib/Sema/CSSyntacticElement.cpp

@@ -74,7 +74,7 @@ public:
     if (auto *DRE = dyn_cast<DeclRefExpr>(expr)) {
       auto *decl = DRE->getDecl();
 
-      if (auto type = CS.getTypeIfAvailable(DRE->getDecl())) {
+      if (auto type = CS.getTypeIfAvailable(decl)) {
         auto &ctx = CS.getASTContext();
         // If this is not one of the closure parameters which
         // is inferrable from the body, let's replace type