Internal lint: suggest is_type_diagnostic_item over match_type where applicable

[ebroto]

changelog: none

[rust-highfive]

r? @yaahc

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[bors]

☔ The latest upstream changes (presumably #6006) made this pull request unmergeable. Please resolve the merge conflicts.

[ghost]

This is a great idea.

Is there any reason to save the path to a diagnostic item at all? I think it might be easier to loop through the lines of utils/path.rs and apply the check there.

Maybe you could make a similar lint to check for lang items as well.

[ebroto]

Is there any reason to save the path to a diagnostic item at all?

Maybe you could make a similar lint to check for lang items as well.

Yeah my initial idea was to get rid of diagnostic items in the paths module, but it's not as straightforward as it could seem. For example, in some cases paths to diagnostic items are put together in a slice with paths to other types, and fed to match_def_path.

But you make me think that maybe we could work on the clippy utils module to expose functions that take a type that could be either a diagnostic item, a lang item or another type, using an enum, and avoid using the relevant rustc API functions directly.
I would prefer to discuss this design in a Zulip thread though (it seems we're moving there) and get some feedback before trying to implement it.

If you agree I would go with merging this before, knowing it only addresses a part of the problem. I think it can be helpful to avoid missing it in the reviews.

[ghost]

If you agree I would go with merging this before, knowing it only addresses a part of the problem. I think it can be helpful to avoid missing it in the reviews.

I think it's an good improvement as is. I'm happy with whatever you and the reviewer decide.

[flip1995]

I agree that we can merge this as is. Doing the same with LangItems would be great. Please address the comment by @giraffate and r=me after that.

[ebroto]

@bors r=flip1995

[bors]

📌 Commit d0b5663 has been approved by flip1995

[bors]

⌛ Testing commit d0b5663 with merge 12ce312...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing 12ce312 to master...