[swift-evolution] [Draft] Allow declaration of abstract functions and properties on classes

[Alex Hoppen]

> You're right that this is currently somewhat convoluted (and someone else mentioned that the extension members may not override the inherited ones, which is obviously another problem). But I think protocols are actually pretty close to what you want already, and we're better off extending them to cover abstract class use cases than extending classes.

I am curious to see a way that protocols can override existing methods, since the protocols are always at the top of the inheritance chain and putting them anywhere else makes them abstract classes by definition.

– Alex