Yep, as far as I understand that's one of the criticisms addressed to Eiffel. Covariance and contravariance in a type hierarchy both have their usefulness in a

Yep, as far as I understand that's one of the criticisms addressed to Eiffel. Covariance and contravariance in a type hierarchy both have their usefulness in a type hierarchy, though. I didn't know about Sather, I'll have a look at it. Thanks for that !