anchor.diff:    group('trace', () {
       test('success', () {
         final lines = <String>[];
  -      expect(trace(identifier, (line) => lines.add(line)).parse('a').isSuccess,
  +      expect(trace(identifier, lines.add).parse('a').isSuccess,
             isTrue);
         expect(lines, [
           'Instance of \'SequenceParser\'',
  
positive.code:     test('failure', () {
        final lines = <String>[];
        expect(
            profile(identifier, (line) => lines.add(line)).parse('1').isFailure,
            isTrue);
        expect(lines, hasLength(4));
        final splitLines = lines.map((row) => row.split('\t'));
  
negative.code:     test('success', () {
        final lines = <String>[];
        expect(
            profile(identifier, lines.add)
                .parse('ab123')
                .isSuccess,
            isTrue);
  