Union types are horrendous in practice because they're non-compositional. None|T is usually disjoint except when it isn't, and it's really easy to forget that case and fail to test it properly.
Having used Scala extensively, None as its own type is very much a mistake; it's not a type that you ever want and it only serves to get in the way.
Having used Scala extensively, None as its own type is very much a mistake; it's not a type that you ever want and it only serves to get in the way.