// Martin: I am not sure this is a solvable problem right now. I'll leave it in pending. // derived from pos/t1001 class A trait B[T <: B[T]] extends A class C extends B[C] class D extends B[D] class Data { // force computing lub of C and D (printLubs enabled:) /* lub of List(D, C) at depth 2 lub of List(D, C) at depth 1 lub of List(D, C) at depth 0 lub of List(D, C) is A lub of List(D, C) is B[_1] forSome { type _1 >: D with C <: A } lub of List(D, C) is B[_2] forSome { type _2 >: D with C{} <: B[_1] forSome { type _1 >: D with C{} <: A } } */ // --> result = WRONG // should be: B[X] forSome {type X <: B[X]} -- can this be done automatically? for now, just detect f-bounded polymorphism and fall back to more coarse approximation val data: List[A] = List(new C, new D) val data2 = List(new C, new D) val data3: List[B[_ <: B[_ <: A]]] = List(new C, new D) // Not yet -- // val data4: List[B[X] forSome { type X <: B[X] }] = List(new C, new D) // :7: error: type mismatch; // found : List[B[_ >: D with C <: B[_ >: D with C <: A]]] // required: List[B[X] forSome { type X <: B[X] }] // val data4: List[B[X] forSome { type X <: B[X] }] = List(new C, new D) // works val data5 = List[B[X] forSome { type X <: B[X] }](new C, new D) }