Selectively disable subsumption in Scala? (correctly type List.contains)

Question

List(\"a\").contains(5)

Because an Int can never be contained in a list of String

Answer 1

I think you misunderstand Martin's solution, it is not B <: Eq, it is B : Eq, which is a shortcut for

def Contains[B >: A](x: B)(implicit ev: Eq[B])

And Eq[X] would then contains a method

def areEqual(a: X, b: X): Boolean

This is not the same as moving the equals method of Any a little lower in the hierarchy, which would indeed solve none of the problem of having it in Any.