Switching on a generic type?

You need the is pattern:

func doSomething<T>(type: T.Type) {
    switch type {
    case is String.Type:
        print("It's a String")
    case is Int.Type:
        print("It's an Int")
    default:
        print("Wot?")
    }
}

Note that the break statements are usually not needed, there is no
“default fallthrough” in Swift cases.