Class Nothing is - together with class Null - at the bottom of the Scala type hierarchy.

Type Nothing is a subtype of every other type (including Null); there exist no instances of this type. Even though type Nothing is empty, it is nevertheless useful as a type parameter. For instance, the Scala library defines a value Nil of type List[Nothing]. Because lists are covariant in Scala, this makes Nil an instance of List[T], for any element type T.