[es6] re-implement rest parameters via desugaring

src/scopes.h

 // 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.
 
 #ifndef V8_SCOPES_H_
 #define V8_SCOPES_H_
 
 #include "src/ast.h"
 #include "src/pending-compilation-error-handler.h"
 #include "src/zone.h"
@@ skipping 471 matching lines @@
 
   // Find the script scope.
   // Used in modules implemenetation to find hosting scope.
   // TODO(rossberg): is this needed?
   Scope* ScriptScope();
 
   // Find the first function, global, or eval scope.  This is the scope
   // where var declarations will be hoisted to in the implementation.
   Scope* DeclarationScope();
 
+  // Find the first non-block declaration scope. This should be either a global,
+  // eval or function top scope. Used for declaring temporaries
+  Scope* TempScope() {
+    Scope* s = DeclarationScope();
+    if (s->is_block_scope()) {
+      s = s->outer_scope();

[rossberg, 2015/07/17 08:38:05]

We may potentially want to use declaration blocks in other places, too. Thus, I
would make this s->outer_scope()->DeclarationScope(), to be a bit more general;
and also remove the assert.

[caitp (gmail), 2015/07/17 15:43:23]

done in refactor

+      DCHECK(s->is_function_scope());
+    }
+    return s;
+  }
+
   Handle<ScopeInfo> GetScopeInfo(Isolate* isolate);
 
   // Get the chain of nested scopes within this scope for the source statement
   // position. The scopes will be added to the list from the outermost scope to
   // the innermost scope. Only nested block, catch or with scopes are tracked
   // and will be returned, but no inner function scopes.
   void GetNestedScopeChain(Isolate* isolate, List<Handle<ScopeInfo> >* chain,
                            int statement_position);
 
   // ---------------------------------------------------------------------------
@@ skipping 261 matching lines @@
   PendingCompilationErrorHandler pending_error_handler_;
 
   // For tracking which classes are declared consecutively. Needed for strong
   // mode.
   int class_declaration_group_start_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPES_H_