anchor.diff:    }
   }
   
  +class _SourceContainer implements SourceContainer {
  +  final String pathPrefix;
  +
  +  _SourceContainer(this.pathPrefix);
  +
  +  @override
  +  bool contains(Source source) => source.fullName.startsWith(pathPrefix);
  +}
  +
   class _Error {
     static final _HAS_FIXES_WHITELIST = [
       HintCode.UNUSED_IMPORT,
  
positive.code:     //   print (folder);
      //   return _resolver;
      // };
      
      _context = builder.buildContext(_sourceDirectory.path);
  
  
  
negative.code: 
        // Delete the files
        changeSet = new ChangeSet();
        sourcesList.forEach((s) {
          changeSet.changedContent(s, null);
          changeSet.removedSource(s);
        });
        // Remove sources implicitly created by imports of non-existing files
        changeSet.removedContainer(new _SourceContainer(pathPrefix));
        // _resolver.clear();
        _context.applyChanges(changeSet);
        _ensureAnalysisDone(_context, _MAX_ANALYSIS_DURATION);
  