Invalid cast causing runtime crash in Swift <= 1.2

invalid-cast.swift

import Foundation


let obj = NSNumber(int: 2)

func correct<T>() -> T? {
  if let val = obj as? T {
    println("matching types")
    return val
  }
  else {
    println("not matching")
  }

  return nil
}

func incorrect<T : NSObject>() -> T? {
  if let val = obj as? T {
    println("matching types")
    return val
  }
  else {
    println("not matching")
  }

  return nil
}



correct() as NSString? // prints "not matching"

incorrect() as NSString? // prints "matching types"