我正在尝试为矩形实现一个动画，以执行模态垂直滑动。然而，当我试图编译代码时，我得到了以下错误“Swift 4表达式类型'@value CGRect'在没有更多上下文的情况下不明确”。我已经将问题与传递给CGRect init值的参数隔离开来，但根据苹果的iOS文档，这些参数应该足以指定我需要设置动画的“框架”视图。

这是我的代码：

func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
    guard
        let fromView = transitionContext.viewController(forKey: .from),
        let toView = transitionContext.viewController(forKey: .to)

    else {
            return
    }
    let containerView = transitionContext.containerView
    containerView.insertSubview((toView.view)!, belowSubview: (fromView.view)!)

    let toFrame = transitionContext.finalFrame(for: toView)

    let screenBounds = UIScreen.main.bounds

    let bottomLeftCorner = CGPoint(x: 0, y: screenBounds.height)

    let finalFrameForVC = CGRect(origin: bottomLeftCorner, size: screenBounds.size)

    UIView.animate(withDuration: 2, delay: 1,
                   options: [], (using: transitionContext.finalFrame(for: fromView)),
        animations: {
            fromView.view.frame = finalFrameForVC
    },
        completion: { _ in
            transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
    })
}