anchor.diff:        case $space:
         case $tab:
         case $lf:
  +        // ignore: invariant_booleans
           if (hasToken) results.add(token.toString());
           hasToken = false;
           token.clear();
  
positive.code: // Copyright 2017, the Dart project authors.  Please see the AUTHORS file
  // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE file.
  
  import 'package:charcode/charcode.dart';
  import 'package:string_scanner/string_scanner.dart';
  
negative.code:         // Section 2.2.2: Enclosing characters in single-quotes ( '' ) shall
          // preserve the literal value of each character within the
          // single-quotes. A single-quote cannot occur within single-quotes.
          final firstQuote = scanner.position - 1;
          while (!scanner.scanChar($single_quote)) {
            _checkUnmatchedQuote(scanner, firstQuote);
            token.writeCharCode(scanner.readChar());
  