Also consider mem::transmute with the invalid_reference_casting lint

[Urgau]

This PR extend the invalid_reference_casting lint with regard to the std::mem::transmute function.

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> $DIR/reference_casting.rs:27:16
   |
LL |     let _num = &mut *std::mem::transmute::<_, *mut i32>(&num);
   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I encourage anyone reviewing this PR to do so without whitespaces.

[rustbot]

r? @b-naber

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[est31]

Does this also detect if you cast to the mutable reference directly, like let _num = std::mem::transmute::<_, & mut i32>(&num)?

[Urgau]

Does this also detect if you cast to the mutable reference directly, like let _num = std::mem::transmute::<_, & mut i32>(&num)?

No, but it's already covered by the mutable-transmutes lint.

[est31]

@bors r+ rollup

[bors]

📌 Commit b517dd5 has been approved by est31

It is now in the queue for this repository.

[bors]

⌛ Testing commit b517dd5 with merge 570601f...

[bors]

☀️ Test successful - checks-actions
Approved by: est31
Pushing 570601f to master...

[rust-timer]

Finished benchmarking commit (570601f): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

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)	3.2%	[3.0%, 3.4%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.6%	[-2.6%, -2.6%]	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: 634.77s -> 634.281s (-0.08%)