feat(manual_assert_eq): new lint

[ada4a]

Resolves #13252
Resurrection of #13333

changelog: [manual_assert_eq]: new lint

[rustbot]

r? @Alexendoo

rustbot has assigned @Alexendoo.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[github-actions]

Lintcheck changes for 154a53b

Lint	Added	Removed	Changed
clippy::manual_assert_eq	140	0	0

This comment will be updated if you push new changes

[samueltardieu]

The suggestion is only valid if the types being compared implement Debug.

View changes since this review

[ada4a]

@rustbot ready

[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[Alexendoo]

We shouldn't lint if there is an assert message provided

[ada4a]

I agree that the suggestion is unfortunate in this case, but in general, a provided assert message can often complement the default one from assert_eq

[ada4a]

Maybe reduce the applicability in this case?

[Alexendoo]

The allows in this and other unrelated tests should go in the top level #![allow] like other lints, they don't need a reason

[ada4a]

In my experience, putting such specific allows (and not things like no_effect, which one really wants to apply to the whole file) on the specific locations that trigger them helps keep the test suite clean, as it's easier to notice when a particular allow becomes unnecessary (this has happened to me more than once). Specifying a reason is also helpful for that.