XCode6 Beta 6: Is this class creation syntax no long valid in swift?

Question

I am referring the answer here: https://stackoverflow.com/a/24061386/58129

The code is reproduced here:

var clazz: NSObject.Type = TestObject.self
var instance : NSObject = clazz()

if let testObject = instance as? TestObject {
    println("yes!")
}

If I tried it in a playground in XCode6 beta6, it throws an exception:

Is it no long valid to instantiate a class by calling T.self()