improvement: Add case keyword completion

[jkciesluk]

connected to #5339

[ckipp01]

You're so fast @jkciesluk! 🚀

[tgodzik]

I wonder if people would find it useful, this is suggested as a last option, so going down is almost the same amount of button clicks as just writing case.

I would rather suggest this if we weren't able to suggest anything else.

How will this behave in the case that is in the linked issues?

Option(1).map{
  c@@
  case Some(a) =>
}

it would be awesome if None was suggested. Having just case would also be nice, but that would be a minimum I would expect to show up.

[jkciesluk]

I think it already suggests None:

Are you thinking about suggesting only not covered cases?

[tgodzik]

I think we should only show a single case if nothing else is shown to the user. Otherwise it's not that useful.

I think it already suggests None:

Do we have a test case for that? I thought this not working was the issue raised?

[jkciesluk]

I thought this not working was the issue raised?

I believe the issue was raised because there was no case completions at all, but this happened because there was no extending classes, just objects with unapply, which we don't check (maybe we could, by looking through object in scope with unapply method and correct argument?).

Do we have a test case for that?

No, I will add it.

I think we should only show a single case if nothing else is shown to the user.
Sure, we can do that

[kasiaMarek]

I'd add the space after case anyway.

[tgodzik]

LGTM