New unreachable! macro.

[erdnaxeli]

This fixes #4749.

[straight-shoota]

It doesn't seem this really needs to be a macro. Making unreachable! a method should be fine. It doesn't do anything that needs to happen at compile time.

I'm not sure why Rust's implementation is a macro. But I also don't know how Rust macros work...

[asterite]

In the original issue the problem was that you needed to raise if an enum value wasn't covered. That's not the case anymore if you use "case in".

There's really no reason to introduce something that's essentially a very simple raise. And raise is more explicit. People will have to learn about this cryptic unreachable! thing when it's just raising.

Let's not merge this.

[erdnaxeli]

In the original issue the problem was that you needed to raise if an enum value wasn't covered. That's not the case anymore if you use "case in".

There's really no reason to introduce something that's essentially a very simple raise. And raise is more explicit. People will have to learn about this cryptic unreachable! thing when it's just raising.

Let's not merge this.

It seems to me that the issue conclusion was exactly the opposite 😅 . But I understand. We can then close this PR and the linked issue too.

[asterite]

Yes, and that happened before we had exhaustive checks built into the language. And the general consensus didn't include my approval.

[erdnaxeli]

So let's close it.