try {
      ClosingFuture<U> derived = new ClosingFuture<>(future);
      state.becomeSubsumedInto(derived.state.closeables);
      return derived;
    } finally {
      reachabilityFence(this);
    }
  }

  private void becomeSubsumedInto(CloseableList otherCloseables) {
    state.becomeSubsumedInto(otherCloseables);
  }

  /**