Getting the Type from a generic

GenericExample-MagicValue.swift

func magicValue<T>() -> T? {
    let type = T.self
    switch type {
    case _ where type == String.self:
        return "hello, world" as? T
    case _ where type == Int.self:
        // Ask for a number and get the answer to life, the universe, and everything
        return 42 as? T
    default:
        return nil
    }
}

let s: String? = magicValue()   // == Optional("hello, world")
let i: Int? = magicValue()      // == Optional(42)
let a: [String]? = magicValue() // == nil