Unnecessary references lint

[obeis]

Close #127724

[rustbot]

r? @Noratrieb

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[rustbot]

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[compiler-errors]

This lint seems really specific to a single kind of expression, and there are plenty of other cases where unnecessary references are created when the user is trying to create a raw pointer. Unless this can be greatly generalized, it doesn't really seem worth adding this.

[compiler-errors]

r? RalfJung

[obeis]

I agree, and my intention is to generalize this lint to cover all unnecessarily created references. Could you please list other cases that you think should be included? I can update this PR to cover them or create an issue to track these cases and mention that they should be added to the unnecessary_refs lint.

[RalfJung]

Sorry, I am swamped. Happy to discuss which cases the lint shoild fire on, but I can't review the implementation. r? compiler

[SparrowLii]

I know little about lints' impls so r? compiler

[RalfJung]

Do we have some people who are our "linting experts"?

[RalfJung]

This lint seems really specific to a single kind of expression, and there are plenty of other cases where unnecessary references are created when the user is trying to create a raw pointer. Unless this can be greatly generalized, it doesn't really seem worth adding this.

Which examples did you have in mind?

A starting point might be to uplift https://rust-lang.github.io/rust-clippy/master/index.html#borrow_as_ptr from cliippy to rustc, as you mention. It is not clear to me what the difference is between that lint and this one.

[traviscross]

Do we have some people who are our "linting experts"?

cc @Urgau

[Urgau]

Happy to take over the review. If @Nadrieril doesn't want to review it of course.

As for the lint it-self, I join @RalfJung that this is lint is currently clippy::borrow_as_ptr, which will need to be dropped from clippy. Look at 1fee1a4 for the changes needed.

As a drive-by, rustc_hir_pretty should not be necessary, a multi-part suggestion should be used instead, with some span manipulation to get the correct spans.

[Nadrieril]

Much appreciated :) r? @Urgau

[rustbot]

Some changes occurred to the intrinsics. Make sure the CTFE / Miri interpreter
gets adapted for the changes, if necessary.

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

[obeis]

I ran x test on my machine, and everything passed. Why is it failing here, and how can I reproduce those errors locally?

[RalfJung]

Maybe try rebasing over the latest master, CI will test your code merged with that and there might be semantic conflicts.

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