swift - 如何制作数组可散列？

Question

我试图在 Swift 3 预览版 6 中Array<String>符合Hashable：

extension Array: Hashable where Element: Hashable {
    public var hashValue: Int {
        var hashValue = 0
        for element in self {
            hashValue ^= element.hashValue
        }
        return hashValue
    }
}

var data = Dictionary<Array<String>, Any>()

但我收到以下错误，不知道为什么：

ERROR at line 4, col 1: extension of type 'Array' with constraints cannot have an inheritance clause
extension Array: Hashable where Element: Hashable {
^    

如何使数组可散列？