anchor.diff:  };
   
   // Rewrite certain Flutter IDs (numbers) using prefix matching.
  -const Map<String, String> identifierPrefixRewrites = <String, String>{
  +const Map<String, String> _identifierPrefixRewrites = <String, String>{
     '1': 'one_',
     '2': 'two_',
     '3': 'three_',
  
positive.code:   }
  
    final String newCodepointsString = newCodepointsFile.readAsStringSync();
    final Map<String, String> newTokenPairMap = _stringToTokenPairMap(newCodepointsString);
  
    final String oldCodepointsString = oldCodepointsFile.readAsStringSync();
    final Map<String, String> oldTokenPairMap = _stringToTokenPairMap(oldCodepointsString);
  
    stderr.writeln('Performing safety checks');
    final bool isSuperset = testIsSuperset(newTokenPairMap, oldTokenPairMap);
  
negative.code: };
  
  // Rewrite certain Flutter IDs (reserved keywords) using exact matching.
  const Map<String, String> _identifierExactRewrites = <String, String>{
    'class': 'class_',
    'new': 'new_',
    'switch': 'switch_',
  