[catnaroek]

> I thought your solution didn't address

FWIW, I didn't propose the original Scala snippet, so it isn't really “my” solution.

> the original covariance/contravariance problem

The problem is precisely preventing what you're trying to do, because it's unsafe.

[shiro]

Ah, ok, I mixed up you with continuational.

For this context, what I'm saying is that if you don't need to extract an apple from a list of fruits, then you can do it safely with inheritance, so whether using inheritance or delegation is irrelevant. Isn't it?

[catnaroek]

If you want to extract an apple from a list of fruits, you need runtime type information (so that you can test whether a particular fruit object happens to be an apple), which has nothing to do with whether your language has inheritance or not. Using runtime type information is a symptom of bad design, though, since it lessens the extent to which you can reason about programs (as pieces of text) by just looking at their types.

[shiro]

I agree with you all. All I say is that suggesting delegation in place of inheritance to address contravariance issue seems off the mark.