anchor.diff:  
     void test_comma() {
       _assertToken(TokenType.COMMA, ",");
  -  }
  -
  -  void test_comment_disabled_multi() {
  -    Scanner scanner =
  -        new _TestScanner(new CharSequenceReader("/* comment */ "));
  -    scanner.preserveComments = false;
  -    Token token = scanner.tokenize();
  -    expect(token, isNotNull);
  -    expect(token.precedingComments, isNull);
     }
   
     void test_comment_generic_method_type_assign() {
  
positive.code:     expect(TokenType.TILDE_SLASH.isUserDefinableOperator, isTrue);
    }
  }
  
  class _TestScanner extends Scanner {
    final ErrorListener listener;
  
    _TestScanner(CharacterReader reader, [this.listener]) : super.create(reader);
  
    @override
    void reportError(
        ScannerErrorCode errorCode, int offset, List<Object> arguments) {
      if (listener != null) {
        listener.errors.add(new TestError(offset, errorCode, arguments));
      }
    }
  }
  
negative.code:     expect(token.precedingComments.next.next.previous,
          same(token.precedingComments.next));
      expect(token.precedingComments.next.next.next, isNull);
    }
  
    void test_comment_multi_unterminated() {
  