anchor.diff:     * [contextMessages] are provided, they will be recorded with the error.
      */
     AnalysisError(this.source, int offset, int length, this.errorCode,
  -      [List<Object> arguments, List<DiagnosticMessage> contextMessages]) {
  +      [List<Object> arguments,
  +      List<DiagnosticMessage> contextMessages = const []]) {
       String message = formatList(errorCode.message, arguments);
       String correctionTemplate = errorCode.correction;
       if (correctionTemplate != null) {
  
positive.code:    */
    AnalysisError.forValues(this.source, int offset, int length, this.errorCode,
        String message, this._correction,
        {List<DiagnosticMessage> contextMessages}) {
      _problemMessage = new DiagnosticMessageImpl(
          filePath: source?.fullName,
          length: length,
  
negative.code:    */
    final ErrorCode errorCode;
  
    /**
     * The message describing the problem.
     */
    DiagnosticMessage _problemMessage;
  
    /**
     * The context messages associated with the problem. This list will be empty
     * if there are no context messages.
     */
    List<DiagnosticMessage> _contextMessages;
  
    /**
  