anchor.diff:    }
   
     final String newCodepointsString = newCodepointsFile.readAsStringSync();
  -  final Map<String, String> newTokenPairMap = _stringToTokenPairMap(newCodepointsString);
  +  final Map<String, String> newTokenPairMap = stringToTokenPairMap(newCodepointsString);
   
     final String oldCodepointsString = oldCodepointsFile.readAsStringSync();
  -  final Map<String, String> oldTokenPairMap = _stringToTokenPairMap(oldCodepointsString);
  +  final Map<String, String> oldTokenPairMap = stringToTokenPairMap(oldCodepointsString);
   
     stderr.writeln('Performing safety checks');
     final bool isSuperset = testIsSuperset(newTokenPairMap, oldTokenPairMap);
  
positive.code:   static String generateFlutterId(String id) {
      String flutterId = id;
      // Exact identifier rewrites.
      for (final MapEntry<String, String> rewritePair in identifierExactRewrites.entries) {
        final String shortId = Icon._generateShortId(id);
        if (shortId == rewritePair.key) {
          flutterId = id.replaceFirst(
            rewritePair.key,
            identifierExactRewrites[rewritePair.key]!,
          );
        }
      }
      // Prefix identifier rewrites.
      for (final MapEntry<String, String> rewritePair in identifierPrefixRewrites.entries) {
        if (id.startsWith(rewritePair.key)) {
          flutterId = id.replaceFirst(
            rewritePair.key,
            identifierPrefixRewrites[rewritePair.key]!,
          );
        }
      }
  
negative.code:   return argParser.parse(args);
  }
  
  Map<String, String> stringToTokenPairMap(String codepointData) {
    final Iterable<String> cleanData = LineSplitter.split(codepointData)
        .map((String line) => line.trim())
        .where((String line) => line.isNotEmpty);
  