anchor.diff:          verify(letter | digit | whitespace, 'abc123 ', '_!@#');
           verify(letter | (digit | whitespace), 'abc123 ', '_!@#');
           verify((letter | digit) | whitespace, 'abc123 ', '_!@#');
  +        verify((letter | digit) | (whitespace | digit), 'abc123 ', '_!@#');
         });
       });
       group('action', () {
  
positive.code:         verify(new CharMatcher.letterOrDigit(), 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890_', '!@# ');
        });
        test('whitespace', () {
          verify(new CharMatcher.whitespace(), ' \n\t', 'abcABC_!@#');
        });
      });
      group('operators', () {
  
negative.code:       test('isChar', () {
          verify(new CharMatcher.isChar('*'), '*', 'abc123_!@# ');
        });
        test('isChar number', () {
          verify(new CharMatcher.isChar(42), '*', 'abc123_!@# ');
        });
        test('isChar invalid', () {
          expect(() => new CharMatcher.isChar('ab'), throwsArgumentError);
        });
        test('inRange', () {
          verify(new CharMatcher.inRange('a', 'c'), 'abc', 'def123_!@# ');
        });
  