[es6] re-implement rest parameters via desugaring

src/scopes.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/bootstrapper.h"
 #include "src/messages.h"
 #include "src/parser.h"
@@ skipping 754 matching lines @@
 
 Scope* Scope::DeclarationScope() {
   Scope* scope = this;
   while (!scope->is_declaration_scope()) {
     scope = scope->outer_scope();
   }
   return scope;
 }
 
 
+Scope* Scope::TempScope() {
+  Scope* scope = this;
+  while (!scope->is_declaration_scope() || scope->is_block_scope()) {
+    scope = scope->outer_scope();
+  }
+  return scope;
+}
+
+
 Handle<ScopeInfo> Scope::GetScopeInfo(Isolate* isolate) {
   if (scope_info_.is_null()) {
     scope_info_ = ScopeInfo::Create(isolate, zone(), this);
   }
   return scope_info_;
 }
 
 
 void Scope::GetNestedScopeChain(Isolate* isolate,
                                 List<Handle<ScopeInfo> >* chain, int position) {
@@ skipping 831 matching lines @@
   bool is_function_var_in_context =
       function_ != NULL && function_->proxy()->var()->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
          2 * num_global_slots() - (is_function_var_in_context ? 1 : 0);
 }
 
 
 int Scope::ContextGlobalCount() const { return num_global_slots(); }
 }  // namespace internal
 }  // namespace v8