Uplift clippy::cast_ref_to_mut lint

[Urgau]

This PR aims at uplifting the clippy::cast_ref_to_mut lint into rustc.

cast_ref_to_mut

ℹ️ The lint has been renamed to invalid_reference_casting in #113422 and #112431

(deny-by-default)

The cast_ref_to_mut lint checks for casts of &T to &mut T without using interior mutability.

Example

fn x(r: &i32) {
    unsafe {
        *(r as *const i32 as *mut i32) += 1;
    }
}

Explanation

Casting &T to &mut T without interior mutability is undefined behavior, as it's a violation of Rust reference aliasing requirements.

---

Mostly followed the instructions for uplifting a clippy lint described here: #99696 (review)

@rustbot label: +I-lang-nominated
r? compiler

---

For Clippy:

changelog: Moves: Uplifted clippy::cast_ref_to_mut into rustc

[rustbot]

The Miri subtree was changed

cc @rust-lang/miri

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

[tmandry]

@rfcbot fcp merge

[rfcbot]

Team member @tmandry has proposed to merge this. The next step is review by the rest of the tagged team members:

• @joshtriplett
• @nikomatsakis
• @pnkfelix
• @scottmcm
• @tmandry

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

cc @rust-lang/lang-advisors: FCP proposed for lang, please feel free to register concerns.
See this document for info about what commands tagged team members can give me.

[scottmcm]

Sadly this wouldn't catch the https://blog.rust-lang.org/2017/02/09/Rust-1.15.1.html#whats-in-1151-stable issue, but still sounds like a good lint.

It would be nice if it could also catch things like

*ptr::from_ref(r).cast_mut() += 1;

but that doesn't need to block accepting this.

@rfcbot reviewed

[nikomatsakis]

@rfcbot reviewed

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

[rustbot]

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

• Stabilizing library features
• Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
• Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
• Changing public documentation in ways that create new stability guarantees
• Changing observable runtime behavior of library APIs

[bors]

☔ The latest upstream changes (presumably #111799) made this pull request unmergeable. Please resolve the merge conflicts.

[Urgau]

@rustbot label -I-lang-nominated

[b-naber]

@bors r+

[bors]

📌 Commit 32d4e1c has been approved by b-naber

It is now in the queue for this repository.

[bors]

⌛ Testing commit 32d4e1c with merge ba1690b...

[bors]

☀️ Test successful - checks-actions
Approved by: b-naber
Pushing ba1690b to master...

[rust-timer]

Finished benchmarking commit (ba1690b): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.7%	[-0.7%, -0.7%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.9%	[2.3%, 3.5%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.5%	[-2.5%, -2.5%]	1
All ❌✅ (primary)	-	-	0

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 644.991s -> 644.818s (-0.03%)