gistfile1.scala

trait Eq[-T] 

def equal[T](left : T, right : T)(implicit eqT : Eq[T]) = true

implicit def eqInt = new Eq[Int]{}

trait List[T]

implicit def eqList[T](implicit eqT : Eq[T]) = new Eq[List[T]] {}

class ListListInt extends List[List[Int]]

def ints = new ListListInt

equal[ListListInt](ints, ints)

equal(ints, ints)

equal[List[List[Int]]](ints, ints)
equal[ListListInt](ints, ints)
equal(ints, ints)