       }
     }
 
-    // result has been determined
-    guard let p = r else { fatalError() }
-    let result = p.pointee
+    // this Deferred is determined
+    let result = r!.pointee
 
     if qos == .unspecified
     {

    {
      let waitQueue = waiters
      if CAS(current: waitQueue, new: nil, target: &waiters)
      {
        // only this thread has the pointer `waitQueue`.
        WaitQueue.notifyAll(queue, waitQueue, result)
        break
      }

      }

      if r != nil
      { // another thread succeeded ahead of this one
        assert(r != p)
        p.deinitialize(count: 1)
        p.deallocate(capacity: 1)
        return false
