anchor.diff:  
   Async:                          'async';
   Await:                          'await';
  +Yield:                          'yield';
   
   /// The following tokens are also considered to be FutureReservedWords
   /// when parsing strict mode
  
positive.code: Package:                        'package' {this.IsStrictMode()}?;
  Protected:                      'protected' {this.IsStrictMode()}?;
  Static:                         'static' {this.IsStrictMode()}?;
  Yield:                          'yield' {this.IsStrictMode()}?;
  
  /// Identifier Names and Identifiers
  
  
negative.code: 
  fragment RegularExpressionBackslashSequence
      : '\\' ~[\r\n\u2028\u2029]
      ;
  