unnecessary_mut_passed: add structured suggestion

[ada4a]

resolves #8943

changelog: [unnecessary_mut_passed]: add structured suggestion

[rustbot]

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[github-actions]

Lintcheck changes for 597d5a5

Lint	Added	Removed	Changed
clippy::unnecessary_mut_passed	0	0	1

This comment will be updated if you push new changes

[ada4a]

@blyxyas friendly ping

[blyxyas]

I haven't forgotten about this PR! Just that I'm preparing a talk and am currently a bit more focused on that. Still this PR was in the next batch to review, so a review will be made in the next few days

Thanks for ping anyways, sometimes I actually forget about some PRs or issues

=^w^=

[ada4a]

All good! Thanks for letting me know, and good luck with the talk:)

[blyxyas]

Great starting point! Just a testing nit and a confirmation to change the sugg message.

[ada4a]

@rustbot ready

[samueltardieu]

Could you also add check for raw pointers? Something like

fn takes_raw_const(a: *const i32) {}
fn takes_raw_mut(a: *mut i32) {}

[…]
    // Raw pointers
    let mut a = 42;
    takes_raw_const(&mut a);
    //~^ unnecessary_mut_passed
    takes_raw_const(&raw mut a);
    takes_raw_mut(&mut a);

The takes_raw_const(&raw mut a) is not covered by this lint though, it could be later added as a new feature.

[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.

[ada4a]

Put the &raw-specific cases into a separate function, because they all don't lint currently. I guess they could be moved back to main once &raw is properly dealt with, but tbh main is barely legible already with all the combinatorial explosion of test cases I added previously...

[blyxyas]

LGTM, thanks! ❤️ The test suite is now great! So exhaustive =^w^=