[es6] re-implement rest parameters via desugaring

src/parser.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_PARSER_H_
 #define V8_PARSER_H_
 
 #include "src/allocation.h"
 #include "src/ast.h"
 #include "src/compiler.h"  // TODO(titzer): remove this include dependency
@@ skipping 1299 matching lines @@
   return parser_->SpreadCallNew(function, args, pos);
 }
 
 
 void ParserTraits::DeclareFormalParameter(
     ParserFormalParameterParsingState* parsing_state, Expression* pattern,
     ExpressionClassifier* classifier, bool is_rest) {
   bool is_duplicate = false;
   bool is_simple_name = pattern->IsVariableProxy();
   DCHECK(parser_->allow_harmony_destructuring() || is_simple_name);
-
+  if (is_rest) parsing_state->has_rest = true;
   const AstRawString* name = is_simple_name
                                  ? pattern->AsVariableProxy()->raw_name()
                                  : parser_->ast_value_factory()->empty_string();
   Variable* var =
       parsing_state->scope->DeclareParameter(name, VAR, is_rest, &is_duplicate);
   parsing_state->AddParameter(var, is_simple_name ? nullptr : pattern);
   if (is_sloppy(parsing_state->scope->language_mode())) {
     // TODO(sigurds) Mark every parameter as maybe assigned. This is a
     // conservative approximation necessary to account for parameters
     // that are assigned via the arguments array.
@@ skipping 13 matching lines @@
   auto* init_block =
       parser_->BuildParameterInitializationBlock(formal_parameters, ok);
   if (!*ok) return;
   if (init_block != nullptr) {
     body->Add(init_block, parser_->zone());
   }
 }
 } }  // namespace v8::internal
 
 #endif  // V8_PARSER_H_