class Test {

  class C { type T; type Coll }

  type T1 = C { type T = Int }

  type T11 = T1 { type Coll = Set[Int] }

  type T2 = C { type Coll = Set[T] }

  type T22 = T2 { type T = Int }

  var x: T11 = _
  var y: T22 = _

  x = y
  y = x

}