Gracefully handle syntax errors in Parser::PatternRewriter.

src/parsing/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_PARSING_PARSER_H_
 #define V8_PARSING_PARSER_H_
 
 #include "src/allocation.h"
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
@@ skipping 814 matching lines @@
       BINDING,
       INITIALIZER,
       ASSIGNMENT,
       ASSIGNMENT_INITIALIZER
     };
 
     PatternContext context() const { return context_; }
     void set_context(PatternContext context) { context_ = context; }
 
     void RecurseIntoSubpattern(AstNode* pattern, Expression* value) {
+      if (!*ok_) return;
+
       Expression* old_value = current_value_;
       current_value_ = value;
       recursion_level_++;
       pattern->Accept(this);
       recursion_level_--;
       current_value_ = old_value;
     }
 
     void VisitObjectLiteral(ObjectLiteral* node, Variable** temp_var);
     void VisitArrayLiteral(ArrayLiteral* node, Variable** temp_var);
@@ skipping 368 matching lines @@
 
 DoExpression* ParserTraits::ParseDoExpression(bool* ok) {
   return parser_->ParseDoExpression(ok);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_H_