[arp242]

> Can you give a real world example that couldn't be solved with interfaces?

There are none, you can always work around them, with the only downside is that you'll move some potential compile-time errors to runtime errors.

But that's the wrong conversation to be having; we could also say "why do we need floats? Everything can be solved with ints too", which is true, but also a lot of work and a poor trade-off. Similar arguments exist for many language features.

So it's a question of trade-offs: how much time will this save people? Will it reduce faults? And what are the costs of adding this? And how do they balance?