check(index != -1)

    calls.removeAt(index)
    this.connection = null

    if (calls.isEmpty()) {
      connection.idleAtNs = System.nanoTime()
      if (connectionPool.connectionBecameIdle(connection)) {
        return connection.socket()
      }
    }

    return null
  }

  private fun timeoutExit(cause: IOException?): IOException? {
    if (timeoutEarlyExit) return cause

    scheduleCloser()
  }

  /**
   * Notify this pool that [connection] has become idle. Returns true if the connection has been
   * removed from the pool and should be closed.
   */
  fun connectionBecameIdle(connection: RealConnection): Boolean {
    connection.assertLockHeld()

    return if (connection.noNewExchanges || maxIdleConnections == 0) {
      connection.noNewExchanges = true