@Override
 public ExitCode build(
     CompileContext context,
     ModuleChunk chunk,
     DirtyFilesHolder<JavaSourceRootDescriptor, ModuleBuildTarget> dirtyFilesHolder,
     OutputConsumer outputConsumer)
     throws ProjectBuildException, IOException {
   if (dirtyFilesHolder.hasRemovedFiles()) {
     final BackwardReferenceIndexWriter writer = BackwardReferenceIndexWriter.getInstance();
     if (writer != null) {
       for (ModuleBuildTarget target : chunk.getTargets()) {
         final Collection<String> files = dirtyFilesHolder.getRemovedFiles(target);
         writer.processDeletedFiles(files);
       }
     }
   }
   return null;
 }
 @Override
 public void buildFinished(CompileContext context) {
   BackwardReferenceIndexWriter.closeIfNeed();
 }
 @Override
 public void buildStarted(CompileContext context) {
   BackwardReferenceIndexWriter.initialize(context);
 }