A type U is a super type of a type V iff it holds that any value of type V is also a value of type U
A type U is a super type of a type V iff it holds that any value of type V is also a value of type U
true if this type is a super type of other
join == union type == smallest shared super type
join == union type == smallest shared super type
meet == intersection type == largest shared sub type
meet == intersection type == largest shared sub type