This essay says that inheritance is harmful and if possible you should “ban inheritance completely”. You see these arguments a lot, as well as things like “prefer composition to inheritance”. A lot of these arguments argue that in practice inheritance has problems. But they don’t preclude inheritance working in another context, maybe with a better language syntax. And it doesn’t explain why inheritance became so popular in the first place. I want to explore what’s fundamentally challenging about inheritance and why we all use it anyway.
That quote from Meyer about contravariance not being “useful” is either a misreading of the cited source (the closest thing to a direct quote is about C++'s lack of variance) or, more charitably, a massive oversimplification. I don’t know Eiffel, but from Meyer’s speech, it sounds like Eiffel lets you choose between something like covariance and something like contravariance for each method. Unfortunately, the second link provided for context seems to be broken.