[es6] enable destructuring rest parameters

src/parsing/parser-base.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_PARSING_PARSER_BASE_H
 #define V8_PARSING_PARSER_BASE_H
 
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
 #include "src/hashmap.h"
@@ skipping 1318 matching lines @@
                                               Token::String(Token::RPAREN));
         return factory()->NewEmptyParentheses(beg_pos);
       } else if (Check(Token::ELLIPSIS)) {
         // (...x)=>x.  The continuation that looks for the => is in
         // ParseAssignmentExpression.
         int ellipsis_pos = position();
         classifier->RecordExpressionError(scanner()->location(),
                                           MessageTemplate::kUnexpectedToken,
                                           Token::String(Token::ELLIPSIS));
         classifier->RecordNonSimpleParameter();
-        Scanner::Location expr_loc = scanner()->peek_location();
-        Token::Value tok = peek();
         ExpressionT expr =
             this->ParseAssignmentExpression(true, classifier, CHECK_OK);
-        // Patterns are not allowed as rest parameters.  There is no way we can
-        // succeed so go ahead and use the convenient ReportUnexpectedToken
-        // interface.
-        if (!Traits::IsIdentifier(expr)) {
-          ReportUnexpectedTokenAt(expr_loc, tok);
-          *ok = false;
-          return this->EmptyExpression();
-        }
         if (peek() == Token::COMMA) {
           ReportMessageAt(scanner()->peek_location(),
                           MessageTemplate::kParamAfterRest);
           *ok = false;
           return this->EmptyExpression();
         }
         Expect(Token::RPAREN, CHECK_OK);
         return factory()->NewSpread(expr, ellipsis_pos);
       }
       // Heuristically try to detect immediately called functions before
@@ skipping 1501 matching lines @@
   bool is_rest = parameters->has_rest;
 
   Token::Value next = peek();
   ExpressionT pattern = ParsePrimaryExpression(classifier, ok);
   if (!*ok) return;
 
   ValidateBindingPattern(classifier, ok);
   if (!*ok) return;
 
   if (!Traits::IsIdentifier(pattern)) {
-    if (is_rest || !allow_harmony_destructuring_bind()) {
+    if (!allow_harmony_destructuring_bind()) {
       ReportUnexpectedToken(next);
       *ok = false;
       return;
     }
     parameters->is_simple = false;
     ValidateFormalParameterInitializer(classifier, ok);
     if (!*ok) return;
     classifier->RecordNonSimpleParameter();
   }
 
@@ skipping 458 matching lines @@
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H