Swift Any

Any can represent an instance of any type at all, including function types.

Any 也可以代表可选性, 如下代码, 说得通, 但不应该.

var a: Int?
let b = a as Any
if b != nil {
    print("b != nil, b == \(b)")
}
// print
b != nil, b == nil

reference: TypeCasting