Scala lower bounds + multiple argument list.

lower-bound.scala

class Sup
class Sub(val element: Int) extends Sup

def test1[B >: Sub](a: Sub, b: B): B = if (a.element < 0) b else a
//                        ||
//                        || difference
//                        ||
//                        \/
def test2[B >: Sub](a: Sub)(b: B): B = if (a.element < 0) b else a

test1(new Sub(1), new Sub(1)) // res17: Sub = Sub@37e5f771
test2(new Sub(1))(new Sub(1)) // res18: Sub = Sub@37900029

test1(new Sub(1), new Sup)    // res19: Sup = Sub@2fa357c9
test2(new Sub(1))(new Sup)    // WTF?!
// <console>:11: error: type mismatch;
//  found   : Sup
//  required: Sub
//               test2(new Sub(1))(new Sup)