@Override
      public void pluginUnloaded(@NotNull IdeaPluginDescriptor pluginDescriptor, boolean isUpdate) {
        // `myIdToDirCache` could retain alien file systems
        clearIdCache();
        // remove alien file system references from myRoots
        for (Iterator<Map.Entry<String, VirtualFileSystemEntry>> iterator = myRoots.entrySet().iterator(); iterator.hasNext(); ) {
          Map.Entry<String, VirtualFileSystemEntry> entry = iterator.next();
          VirtualFileSystemEntry root = entry.getValue();
          if (VirtualFileManager.getInstance().getFileSystem(root.getFileSystem().getProtocol()) == null) {
            // the file system must have been unregistered
            iterator.remove();//TODO RC: but entry in a .idToDirCache.myIdToRootCache -- still remains?
          }
        }
      }
@Override
      public void pluginUnloaded(@NotNull IdeaPluginDescriptor pluginDescriptor, boolean isUpdate)