anchor.diff:      correction: "Try extending 'Struct' or 'Union' directly.",
       uniqueName: 'SUBTYPE_OF_STRUCT_CLASS_IN_WITH',
     );
  -
  -  @override
  -  final ErrorType type;
   
     /// Initialize a newly created error code to have the given [name]. If
     /// [uniqueName] is provided, then it will be used to construct the unique
  
positive.code: 
    @override
    ErrorSeverity get errorSeverity => type.severity;
  }
  
negative.code:     bool hasPublishedDocs = false,
      required String message,
      required String name,
      String? uniqueName,
    }) : super(
            correction: correction,
            hasPublishedDocs: hasPublishedDocs,
            message: message,
  