internal: Fix Clippy warnings and replace some if lets with match

[lunacookies]

I decided to try fixing a bunch of Clippy warnings. I am aware of this project’s opinion of Clippy (I have read both rust-lang/clippy#5537 and rust-analyzer/rowan#57 (comment)), so I totally understand if part of or the entirety of this PR is rejected. In particular, I can see how the semicolons and if let vs match commits provide comparatively little benefit when compared to the ensuing churn.

I tried to separate each kind of change into its own commit to make it easier to discard certain changes. I also only applied Clippy suggestions where I thought they provided a definite improvement to the code (apart from semicolons, which is IMO more of a formatting/consistency question than a linting question). In the end I accumulated a list of 28 Clippy lints I ignored entirely.

Sidenote: I should really have asked about this on Zulip before going through all 1,555 if lets in the codebase to decide which ones definitely look better as match :P

[Veykril]

The changes look good to me.
Though I am personally not a fan of "Replace if let Some(_) = foo with if let foo.is_some()", I prefer pattern matches. Then again my preference doesn't align with our style guide in some ways anyways which I assume this might apply to as well(would be a good addition to it at least)

Will wait for another opinion before merging.

[lunacookies]

To ensure the semicolon changes remain in future, would it be good to add a check just for that lint to CI?

Edit: one way this could be done is by adding a test that checks the exit code of cargo clippy -- --allow clippy::all --deny clippy::semicolon_if_nothing_returned to tidy.rs.

[lunacookies]

Sorry for the force push, just noticed I wrote if let foo.is_some() instead of if foo.is_some() in the commit message.

[Veykril]

To ensure the semicolon changes remain in future, would it be good to add a check just for that lint to CI?

I feel like that might become very annoying(wish rustfmt would just fix that since it's a change that wouldn't change semantics anyways).

[lunacookies]

Hmm, good point. I too wish rustfmt would handle adding semicolons in these places automatically. Doing this kind of formatting requires type information, so I can definitely see why it hasn’t been implemented. Is there any point in making semicolons consistent now if they’ll just regress over time?

[Veykril]

Right that does require type info...

I mean it doesn't hurt making these consistent every now and then if its just running a clippy fix. At least its better than having these accumulate more and more I feel like.

[lunacookies]

Unfortunately fixing semicolons is not something done by cargo clippy --fix at the moment. I took a short look through the Clippy source code, but I can’t find anything that specifically implements fixes for certain lints.

[Veykril]

Oh that's a shame, sounds like something that could have a simple fix to it.

I'll go ahead and merge this now before this might run into merge conflicts as this applies none of the weird clippy lints.
bors r+

[bors]

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