Tracking issue for invalid_reference_casting

This is a tracking issue for the lint invalid_reference_casting, which was uplifted from Clippy's cast_ref_to_mut lint in https://github.com/rust-lang/rust/pull/111567.

This lint is deny-by-default, i.e. #![deny(invalid_reference_casting)].

Status

This lint was uplifted directly from Clippy, but shortly after that a bug in the lint was reported: https://github.com/rust-lang/rust/issues/124685. Currently we are working on eliminating all forms of this issue.

Steps

• @saethlin is doing some investigation into how this lint is tripped across the ecosystem by crawling crater results.

Open Questions

The lint currently hunts for an expression that represents the backing allocation, then if it encounters a pattern known to produce false positives, we punt on reporting that case. Should we invert the logic and be silent by default instead?

Implementation history

https://github.com/rust-lang/rust/pull/111567
https://github.com/rust-lang/rust/pull/124761
https://github.com/rust-lang/rust/pull/124908
https://github.com/rust-lang/rust/pull/124978

Start by reading the linked implementation pull requests, especially the report in issue 124685, and review the crater investigation described here. Done would require addressing the lint's false positives and resolving the open question about whether its reporting logic should be inverted.