[async-await] (simpler) fix for Return in try/finally in async functions

src/ast/scopes.cc

Index: src/ast/scopes.cc
diff --git a/src/ast/scopes.cc b/src/ast/scopes.cc
index bd91e16a5220cccfab9ccb59f7eee7464dedac52..10eb8a4d41ef00307827317ca187e0bef2359b12 100644
--- a/src/ast/scopes.cc
+++ b/src/ast/scopes.cc
@@ -298,6 +298,8 @@ void DeclarationScope::SetDefaults() {
   function_ = nullptr;
   arguments_ = nullptr;
   this_function_ = nullptr;
+  generator_object_ = nullptr;
+  promise_ = nullptr;
   should_eager_compile_ = false;
   was_lazily_parsed_ = false;
 #ifdef DEBUG
@@ -703,6 +705,21 @@ Variable* DeclarationScope::DeclareFunctionVar(const AstRawString* name) {
   return function_;
 }
 
+Variable* DeclarationScope::DeclareGeneratorObjectVar(
+    const AstRawString* name) {
+  DCHECK(is_function_scope() || is_module_scope());
+  DCHECK_NULL(generator_object_);
+  generator_object_ = NewTemporary(name);
+  return generator_object_;
+}
+
+Variable* DeclarationScope::DeclarePromiseVar(const AstRawString* name) {
+  DCHECK(is_function_scope());
+  DCHECK_NULL(promise_);
+  promise_ = NewTemporary(name);
+  return promise_;
+}
+
 bool Scope::HasBeenRemoved() const {
   if (sibling() == this) {
     DCHECK_NULL(inner_scope_);