[parser] Fix scopes in rewriting of for-of and destructuring assignments.

src/ast/scopes.cc

Index: src/ast/scopes.cc
diff --git a/src/ast/scopes.cc b/src/ast/scopes.cc
index c150336668545eb1a8bf78b3af3823f70bb476c1..46591678f90896506d6e4cec86093b5c489e8b2e 100644
--- a/src/ast/scopes.cc
+++ b/src/ast/scopes.cc
@@ -636,6 +636,35 @@ Variable* DeclarationScope::DeclareFunctionVar(const AstRawString* name) {
   return function_;
 }
 
+bool Scope::HasBeenRemoved() const {
+  // TODO(neis): Store this information somewhere instead of calculating it.
+
+  if (!is_block_scope() || is_declaration_scope()) return false;
+
+  Scope* parent = outer_scope();
+  if (parent == nullptr) {
+    DCHECK(is_script_scope());
+    return false;
+  }
+
+  Scope* sibling = parent->inner_scope();
+  for (; sibling != nullptr; sibling = sibling->sibling()) {
+    if (sibling == this) return false;
+  }
+
+  DCHECK_NULL(inner_scope_);
+  return true;
+}
+
+Scope* Scope::GetUnremovedScope() {
+  Scope* scope = this;
+  while (scope != nullptr && scope->HasBeenRemoved()) {
+    scope = scope->outer_scope();
+  }
+  DCHECK_NOT_NULL(scope);
+  return scope;
+}
+
 Scope* Scope::FinalizeBlockScope() {
   DCHECK(is_block_scope());