anchor.diff:  import 'hitmap.dart';
   
   const _retryInterval = Duration(milliseconds: 200);
  +const _debugTokenPositions = bool.fromEnvironment('DEBUG_COVERAGE');
   
   /// Collects coverage for all isolates in the running VM.
   ///
  
positive.code:     final line = _getLineFromTokenPos(script, tokenPos);
  
      if (line == null) {
        stderr.writeln(
            'tokenPos $tokenPos in function ${funcRef.name} has no line mapping '
            'for script ${script.uri!}');
        return;
      }
      hits.funcNames![line] = funcName;
  
negative.code:       for (final pos in tokenPositions) {
          final line = reportLines ? pos : _getLineFromTokenPos(script!, pos);
          if (line == null) {
            if (_debugTokenPositions) {
              stderr.write(
                  'tokenPos $pos has no line mapping for script $scriptUri');
            }
            continue;
          }
          body(line);
  