It's the other way around: null needs to be a subtype of MyType, not a supertype: anywhere I can pass a MyType I should be able to pass a null. You could get m

It's the other way around: null needs to be a subtype of MyType, not a supertype: anywhere I can pass a MyType I should be able to pass a null. You could get most of the way to the blog post's outcomes by simply adding a few methods to Object (is(Not)Null, primarily) and having null be a magic (because it's all classes and none) instance that will NPE on all but the few defined Object methods, I think, but none of that answers the burning question of _why_ that I feel the article doesn't really address.