anchor.diff:        output.write(loadOperation);
       }
       output.write("};\n");
  -    output.write("\nMessageLookupByLibrary _findExact(String localeName) {\n"
  +    output.write(
  +        "\nMessageLookupByLibrary$orNull _findExact(String localeName) {\n"
           "  switch (localeName) {\n");
       for (var rawLocale in allLocales) {
         var locale = Intl.canonicalizedLocale(rawLocale);
  
positive.code:   String prologue(locale) =>
        super.prologue(locale) +
        '''
    String evaluateMessage(translation, List<dynamic> args) {
      return evaluateJsonTemplate(translation, args);
    }
  ''';
  
negative.code: ///   * \['Intl.gender', String gender, (templates for female, male, other)\]
  ///   * \['Intl.select', String choice, { 'case' : template, ...} \]
  ///   * \['text alternating with ', 0 , ' indexes in the argument list'\]
  String$orNull evaluateJsonTemplate(dynamic input, List<dynamic> args) {
    if (input == null) return null;
    if (input is String) return input;
    if (input is int) {
  