[es6] Re-implement rest parameters via desugaring.

src/preparser.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_PREPARSER_H
 #define V8_PREPARSER_H
 
 #include "src/v8.h"
 
 #include "src/bailout-reason.h"
@@ skipping 15 matching lines @@
   kFunctionNameValidityUnknown
 };
 
 
 struct FormalParametersBase {
   explicit FormalParametersBase(Scope* scope) : scope(scope) {}
   Scope* scope;
   bool has_rest = false;
   bool is_simple = true;
   int materialized_literals_count = 0;
+  int rest_array_literal_index = 0;
 };
 
 
 // Common base class shared between parser and pre-parser. Traits encapsulate
 // the differences between Parser and PreParser:
 
 // - Return types: For example, Parser functions return Expression* and
 // PreParser functions return PreParserExpression.
 
 // - Creating parse tree nodes: Parser generates an AST during the recursive
@@ skipping 3601 matching lines @@
   if (!allow_harmony_destructuring() && !Traits::IsIdentifier(pattern)) {
     ReportUnexpectedToken(next);
     *ok = false;
     return;
   }
 
   if (parameters->is_simple) {
     parameters->is_simple = !is_rest && Traits::IsIdentifier(pattern);
   }
   parameters->has_rest = is_rest;
-  if (is_rest && !Traits::IsIdentifier(pattern)) {
-    ReportUnexpectedToken(next);
-    *ok = false;
-    return;
+  if (is_rest) {
+    if (!Traits::IsIdentifier(pattern)) {
+      ReportUnexpectedToken(next);
+      *ok = false;
+      return;
+    }
+    parameters->rest_array_literal_index =
+        function_state_->NextMaterializedLiteralIndex();
   }
   Traits::AddFormalParameter(parameters, pattern, is_rest);
 }
 
 
 template <class Traits>
 void ParserBase<Traits>::ParseFormalParameterList(
     FormalParametersT* parameters, ExpressionClassifier* classifier, bool* ok) {
   // FormalParameters[Yield,GeneratorParameter] :
   //   [empty]
@@ skipping 359 matching lines @@
       *ok = false;
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H