feat: On type format '(', by adding closing ')' automatically

[SomeoneToIgnore]

If I understand right, () can surround pretty much the same {} can, so add another on type formatting pair for convenience: sometimes it's not that pleasant to write parenthesis in Some(2).map(|i| (i, i+1)) cases and I would prefer r-a to do that for me.

One note: currently,

rust-analyzer/crates/rust-analyzer/src/handlers/request.rs

Line 357 in b06503b

stdx::never!(snippet_edit.is_none(), "on type formatting shouldn't use structured snippets");

fires always.
Should we remove the assertion entirely now, since apparently things work in release despite that check?

[DropDemBits]

Should we remove the assertion entirely now, since apparently things work in release despite that check?

Ah, I was the one who added that assert in, and only realized now that this should be a stdx::always instead of a stdx::never 😅

More context on this assert

I originally added this assert since structured snippets add in placeholders & tabstops later on instead of embedding them directly, and I didn't think it was worth it right now to port the on-type formatting to structured snippets as it only uses one tabstop in a fixed location.

[SomeoneToIgnore]

Thank you, works much better with the different assert 🙂

I've pushed the commit here, but feel free to create a separate PR, you have better context and can describe it better.

[bors]

☔ The latest upstream changes (presumably #15542) made this pull request unmergeable. Please resolve the merge conflicts.

[Veykril]

Now I wonder, we might as well add [ to the mix here no?

[Veykril]

Well we can do that in separate PR, but I think that should work in all positions there likewise.
@bors r+

[bors]

📌 Commit da78617 has been approved by Veykril

It is now in the queue for this repository.

[bors]

⌛ Testing commit da78617 with merge 77b359a...

[SomeoneToIgnore]

Now I wonder, we might as well add [ to the mix here no?

I personally rarely index something nested with this, so was afraid to add it myself.
Also, was not sure if it's the same as ( rule-wise to apply its counterpart?
Anyway, not sure if very requested feature, so I restrained from bloating the PR.

Ideally, I'd add | since typing closures is sometimes hard, but that needs a but different set of rules.

[Veykril]

I was more thinking of arrays than indexing here, unsure whether its useful though.

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing 77b359a to master...