anchor.diff:        args.add('disallowNullValues: $disallowNullKeyLiteral');
       }
   
  -    if (args.isNotEmpty) {
  -      _buffer.writeln('${' ' * indent}\$checkKeys(json, ${args.join(', ')});');
  -    }
  -  }
  -
  -  String _deserializeForField(FieldElement field,
  -      {ParameterElement ctorParam, bool checkedProperty}) {
  +    if (args.isEmpty) {
  +      return '';
  +    } else {
  +      return '\$checkKeys(json, ${args.join(', ')});\n';
  +    }
  +  }
  +
  +  String _deserializeForField(
  +    FieldElement field, {
  +    ParameterElement ctorParam,
  +    bool checkedProperty,
  +  }) {
       checkedProperty ??= false;
       final jsonKeyName = safeNameAccess(field);
       final targetType = ctorParam?.type ?? field.type;
  
positive.code:           ..write(');');
        }
  
        _buffer.write('''\n    return val;
    }''');
  
        final fieldKeyMap = Map.fromEntries(data.usedCtorParamsAndFields
  
negative.code: }
  
  abstract class DecodeHelper implements HelperCore {
    CreateFactoryResult createFactory(
      Map<String, FieldElement> accessibleFields,
      Map<String, String> unavailableReasons,
    ) {
      assert(config.createFactory);
      final buffer = StringBuffer();
  
      final mapType = config.anyMap ? 'Map' : 'Map<String, dynamic>';
      buffer.write('$targetClassReference '
          '${prefix}FromJson${genericClassArgumentsImpl(true)}'
          '($mapType json) {\n');
  
  