Is it possible to set a property on UIView via Swift 4 KeyPaths in an extension?

I'm trying to create a set method on UIView via an extension that will allow me to set a color via the new Swift 4 KeyPaths. If I do the following I get the error Cannot assign to immutable expression of type 'UIColor?'

extension UIView {
    func set(color: UIColor, forKeyPath path: KeyPath<UIView, UIColor?>) {
        self[keyPath: path] = color //  Error: Cannot assign to immutable expression of type 'UIColor?'
    }
}
view.set(color: .white, forKeyPath: \.backgroundColor)

If I use this outside of an extension it works fine:

let view = UIView()
let path = \UIView.backgroundColor
view[keyPath: path] = .white // Works fine

Also using the old style of KeyPath works fine:

extension UIView {
    func set(color: UIColor, forKeyPath path: String) {
        self.setValue(color, forKey: path)
    }
}
view.set(color: .white, forKeyPath: #keyPath(UIView.backgroundColor))

Thanks for any help.