[cousin_it]

That seems like a problem with inheritance + mutability, not inheritance on its own. After all, if B is a subtype of A, then we can make List[B] a subtype of List[A] as long as lists are immutable. Appending an A to List[B] returns List[A], what's the problem? :-) In fact some ML style languages (like OCaml) do have inheritance and it works fine with generics. Some generic types (like lists) will be covariant, others (like comparators) will be contravariant, combinations of the two will be invariant, and it all can be automatically inferred.

Which of course doesn't change the fact that imperative languages trying to combine generics + inheritance + mutability are in for a world of hurt.

[tgb]

The same problem happens with immutable types. Does a function of type Int -> A extend a function type Int -> B? How about A -> Int extending B -> Int? The answers to these are opposite.