anchor.diff:              boundaryKey = s.substring(RESULT_OUTPUT_SPACE.length);
             }
           } else {
  -          if (s.startsWith(boundaryKey)) {
  +          if (s.startsWith(boundaryKey!)) {
               boundaryKey = null;
               receivedResult.sendPort.send(true);
             }
  
positive.code: // for details. All rights reserved. Use of this source code is governed by a
  // BSD-style license that can be found in the LICENSE.md file.
  
  // @dart = 2.9
  // ignore_for_file: empty_catches
  
  import 'dart:async';
  
negative.code:       '--incremental',
      ];
  
      late Directory tempDir;
      setUp(() {
        tempDir = Directory.systemTemp.createTempSync();
      });
  