protected final def link()

in util-core/src/main/scala/com/twitter/util/Promise.scala [880:909]

• 24 lines of code
• 15 McCabe index (conditional complexity)

  protected final def link(target: Promise[A]): Unit = {
    if (this eq target) return

    state match {
      case s: Transforming[A] =>
        if (!cas(s, target)) link(target)
        else target.forwardInterruptsTo0(s.other, s.waitq)

      case waitq: WaitQueue[A] =>
        if (!cas(waitq, target)) link(target)
        else target.continue(waitq)

      case value: Try[A] /* Done */ =>
        if (!target.updateIfEmpty(value) && value != Await.result(target)) {
          throw new IllegalArgumentException("Cannot link two Done Promises with differing values")
        }

      case s: Interruptible[A] =>
        if (!cas(s, target)) link(target)
        else target.setInterruptHandler0(s.handler, s.waitq)

      case p: Promise[A] /* Linked */ =>
        if (cas(p, target)) p.link(target)
        else link(target)

      case s: Interrupted[A] =>
        if (!cas(s, target)) link(target)
        else target.raise0(s.signal, s.waitq)
    }
  }