LinkedList<E> (@NotNull DocumentReference r) { LinkedList<E> result; VirtualFile file = r.getFile(); if (file.isInLocalFileSystem()) { result = myDocumentStacks.computeIfAbsent(r, __ -> new LinkedList<>()); } else { result = addWeaklyTrackedEmptyStack(file, myNonlocalVirtualFilesWithStacks); } return result; }