Improvement for equatable_if_let

[nahuakang]

fixes #9221

This PR makes sure that enums or structs not implementing PartialEq trait but still using the if let patterns can be linted to be rewritten with matches!.

If you added a new lint, here's a checklist for things that will be
checked during review or continuous integration.

• Followed [lint naming conventions][lint_naming]
• Added passing UI tests (including committed .stderr file)
• cargo test passes locally
• Executed cargo dev update_lints
• Added lint documentation
• Run cargo dev fmt

---

changelog: Improve [equatable_if_let] with additional matches! suggestions.

[rust-highfive]

r? @flip1995

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[dswij]

Thanks for the PR! This looks good to me.

I'll wait for @flip1995's review if there is any concern with merging this. Particularly, I'm not entirely sure if there's any scenario where we don't want to suggest matches!.

[dswij]

Just one comment, though, @nahuakang can you help to write the changelog field in the PR description

[nahuakang]

@flip1995 Btw when you have time please take a look here :)

[dswij]

Actually @nahuakang, I found a discussion for this very issue #7777 - and it's unresolved yet.

Apologies for just finding this out after you made this PR 😟

[nahuakang]

@dswij No problem :) Thanks for finding it out. So what's the status for either PR? Should I close mine in favor of the other or adjust something?

[dswij]

@dswij No problem :) Thanks for finding it out. So what's the status for either PR? Should I close mine in favor of the other or adjust something?

Seems like the ongoing discussion is not for the matches! case although the consensus there is somewhat on making matches! as a new lint rather than an improvement of equatable_if_let.

I will try to bring this up in Zulip.

[flip1995]

The discussion in the other PR is not really affected by this change, so I'll merge it like this.

Wow, I'm really behind on reviews (this is already from 2 months ago). Sorry about that.

@bors r+

[bors]

📌 Commit 4eaadd6 has been approved by flip1995

It is now in the queue for this repository.

[bors]

⌛ Testing commit 4eaadd6 with merge 628a79d...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing 628a79d to master...