bezierpath视图上的阴影为角落添加了奇怪的笔触

import UIKit

class CustomView: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setup()
    }
    
    private func setup() {
        let shapeLayer = CAShapeLayer()
        shapeLayer.path = UIBezierPath(rect: bounds).cgPath
        
        // 设置阴影属性
        shapeLayer.shadowColor = UIColor.black.cgColor
        shapeLayer.shadowOffset = CGSize(width: 0, height: 2)
        shapeLayer.shadowOpacity = 0.5
        shapeLayer.shadowRadius = 4
        
        // 将CAShapeLayer作为阴影的mask
        layer.mask = shapeLayer
    }
}