Consider returning `Result` from get(_mut)::<Component>() on an entity

[Shatur]

What problem does this solve or what need does it fill?

Entity(Mut/World/WorldMut)::get_mut returns Option which doesn't play nicely with Result: requires writing an error message that entity x missing component y. Also get_mut variant doesn't allow to capture the entity because it's already mutably borrowed.

What solution would you like?

Return Result instead.

[greeble-dev]

I've labelled as S-Needs-Design because I'm unsure what the Result would contain, and whether there might be performance concerns.

[Shatur]

I think Result::Err should contain a unit struct. It would be basically identical to Option, but with a printable error.