[es6] Correct parsing of regular expression literal flags.

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/bailout-reason.h"
 #include "src/expression-classifier.h"
 #include "src/func-name-inferrer.h"
@@ skipping 1232 matching lines @@
   explicit PreParserFactory(void* unused_value_factory) {}
   PreParserExpression NewStringLiteral(PreParserIdentifier identifier,
                                        int pos) {
     return PreParserExpression::Default();
   }
   PreParserExpression NewNumberLiteral(double number,
                                        int pos) {
     return PreParserExpression::Default();
   }
   PreParserExpression NewRegExpLiteral(PreParserIdentifier js_pattern,
-                                       PreParserIdentifier js_flags,
-                                       int literal_index,
-                                       bool is_strong,
-                                       int pos) {
+                                       int js_flags, int literal_index,
+                                       bool is_strong, int pos) {
     return PreParserExpression::Default();
   }
   PreParserExpression NewArrayLiteral(PreParserExpressionList values,
                                       int literal_index,
                                       bool is_strong,
                                       int pos) {
     return PreParserExpression::ArrayLiteral();
   }
   PreParserExpression NewArrayLiteral(PreParserExpressionList values,
                                       int first_spread_index, int literal_index,
@@ skipping 952 matching lines @@
   if (!scanner()->ScanRegExpPattern(seen_equal)) {
     Next();
     ReportMessage(MessageTemplate::kUnterminatedRegExp);
     *ok = false;
     return Traits::EmptyExpression();
   }
 
   int literal_index = function_state_->NextMaterializedLiteralIndex();
 
   IdentifierT js_pattern = this->GetNextSymbol(scanner());
-  if (!scanner()->ScanRegExpFlags()) {
+  Maybe<RegExp::Flags> flags = scanner()->ScanRegExpFlags();
+  if (flags.IsNothing()) {
     Next();
     ReportMessage(MessageTemplate::kMalformedRegExpFlags);
     *ok = false;
     return Traits::EmptyExpression();
   }
-  IdentifierT js_flags = this->GetNextSymbol(scanner());
+  int js_flags = flags.FromJust();
   Next();
   return factory()->NewRegExpLiteral(js_pattern, js_flags, literal_index,
                                      is_strong(language_mode()), pos);
 }
 
 
 #define CHECK_OK  ok); \
   if (!*ok) return this->EmptyExpression(); \
   ((void)0
 #define DUMMY )  // to make indentation work
@@ skipping 2008 matching lines @@
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PREPARSER_H