Method become

future-java/src/main/java/io/trane/future/Promise.java:209–212

Becomes another future. This and result become the same: both are completed with the same result and both receive the same interrupt signals. @param result the future to become.

(final Future<T> result)

   * @param result  the future to become.
   */
  public final void become(final Future<T> result) {
    if (!becomeIfEmpty(result))
      throw new IllegalStateException("Can't set result " + result + " for promise with state " + state);
  }

  /**
   * Becomes another future only if this promise is undefined. This and result