internal var queue: TaskQueue? = null

  /** Undefined unless this is in [TaskQueue.futureTasks]. */
  internal var nextExecuteNanoTime = -1L

  /** Returns the delay in nanoseconds until the next execution, or -1L to not reschedule. */
  abstract fun runOnce(): Long

  internal fun initQueue(queue: TaskQueue) {
    if (this.queue === queue) return

    check(this.queue === null) { "task is in multiple queues" }
    this.queue = queue
  }

        taskRunner.logger.taskLog(task, this) { "already scheduled" }
        return false
      }
      futureTasks.removeAt(existingIndex) // Already scheduled later: reschedule below!
    }
    task.nextExecuteNanoTime = executeNanoTime
    taskRunner.logger.taskLog(task, this) {
      if (recurrence) {
        "run again after ${formatDuration(executeNanoTime - now)}"
      } else {