for (Listener listener : listeners) {
      listener.execute();
    }
    listeners = null;
  }

  protected void afterDone() {}

  @Override
  protected final Throwable tryInternalFastPathGetFailure() {
    if (this instanceof Trusted) {
      return state == State.FAILURE ? throwable : null;
    }
    return null;
  }

  final void maybePropagateCancellationTo(@Nullable Future<?> related) {

    node.thread = null; // mark as 'deleted'
    restart:
    while (true) {
      Waiter pred = null;
      Waiter curr = waiters;
      if (curr == Waiter.TOMBSTONE) {
        return; // give up if someone is calling complete
      }
      Waiter succ;
      while (curr != null) {
        succ = curr.next;
        if (curr.thread != null) { // we aren't unlinking this node, update pred.