WTF Swift generics?

generics.swift

#!/usr/bin/env xcrun swift

import Foundation

class Base {
}

class Sub : Base {
}

func create<T : Base>() -> T {
  println("param is: " + NSStringFromClass(T))
  return T()
}

let o1: Sub = create()
println("result is: " + NSStringFromClass(o1.dynamicType))

FWIW

let o2: Sub = Base()

correctly leads to

error: 'Base' is not convertible to 'Sub'

Submitted as a radar: http://www.openradar.me/19357437