Add a flag for legacy const semantics

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 81 matching lines @@
         allow_lazy_(false),
         allow_natives_(false),
         allow_harmony_arrow_functions_(false),
         allow_harmony_sloppy_(false),
         allow_harmony_computed_property_names_(false),
         allow_harmony_rest_params_(false),
         allow_harmony_spreadcalls_(false),
         allow_harmony_destructuring_(false),
         allow_harmony_spread_arrays_(false),
         allow_harmony_new_target_(false),
-        allow_strong_mode_(false) {}
+        allow_strong_mode_(false),
+        allow_legacy_const_(true) {}
 
 #define ALLOW_ACCESSORS(name)                           \
   bool allow_##name() const { return allow_##name##_; } \
   void set_allow_##name(bool allow) { allow_##name##_ = allow; }
 
   ALLOW_ACCESSORS(lazy);
   ALLOW_ACCESSORS(natives);
   ALLOW_ACCESSORS(harmony_arrow_functions);
   ALLOW_ACCESSORS(harmony_sloppy);
   ALLOW_ACCESSORS(harmony_computed_property_names);
   ALLOW_ACCESSORS(harmony_rest_params);
   ALLOW_ACCESSORS(harmony_spreadcalls);
   ALLOW_ACCESSORS(harmony_destructuring);
   ALLOW_ACCESSORS(harmony_spread_arrays);
   ALLOW_ACCESSORS(harmony_new_target);
   ALLOW_ACCESSORS(strong_mode);
+  ALLOW_ACCESSORS(legacy_const);
 #undef ALLOW_ACCESSORS
 
   bool allow_harmony_modules() const { return scanner()->HarmonyModules(); }
   bool allow_harmony_unicode() const { return scanner()->HarmonyUnicode(); }
 
   void set_allow_harmony_modules(bool a) { scanner()->SetHarmonyModules(a); }
   void set_allow_harmony_unicode(bool a) { scanner()->SetHarmonyUnicode(a); }
 
  protected:
   enum AllowRestrictedIdentifiers {
@@ skipping 355 matching lines @@
     return Token::Precedence(token);
   }
 
   typename Traits::Type::Factory* factory() {
     return function_state_->factory();
   }
 
   LanguageMode language_mode() { return scope_->language_mode(); }
   bool is_generator() const { return function_state_->is_generator(); }
 
+  bool allow_const() {
+    return is_strict(language_mode()) || allow_legacy_const();
+  }
+
   // Report syntax errors.
   void ReportMessage(MessageTemplate::Template message, const char* arg = NULL,
                      ParseErrorType error_type = kSyntaxError) {
     Scanner::Location source_location = scanner()->location();
     Traits::ReportMessageAt(source_location, message, arg, error_type);
   }
 
   void ReportMessageAt(Scanner::Location location,
                        MessageTemplate::Template message,
                        ParseErrorType error_type = kSyntaxError) {
@@ skipping 277 matching lines @@
   bool allow_natives_;
   bool allow_harmony_arrow_functions_;
   bool allow_harmony_sloppy_;
   bool allow_harmony_computed_property_names_;
   bool allow_harmony_rest_params_;
   bool allow_harmony_spreadcalls_;
   bool allow_harmony_destructuring_;
   bool allow_harmony_spread_arrays_;
   bool allow_harmony_new_target_;
   bool allow_strong_mode_;
+  bool allow_legacy_const_;
 };
 
 
 class PreParserIdentifier {
  public:
   PreParserIdentifier() : type_(kUnknownIdentifier) {}
   static PreParserIdentifier Default() {
     return PreParserIdentifier(kUnknownIdentifier);
   }
   static PreParserIdentifier Eval() {
@@ skipping 3160 matching lines @@
       *ok = false;
       return;
     }
     has_seen_constructor_ = true;
     return;
   }
 }
 } }  // v8::internal
 
 #endif  // V8_PREPARSER_H