Re: [PATCH v7 7/7] rust: enable `clippy::ref_as_ptr` lint

Benno Lossin
2025-03-26T22:15:53Z

On Wed Mar 26, 2025 at 11:09 PM CET, Tamir Duberstein wrote:
> On Wed, Mar 26, 2025 at 5:09 PM Benno Lossin <benno.lossin@proton.me> wrote:
>> On Wed Mar 26, 2025 at 8:06 PM CET, Tamir Duberstein wrote:
>> > On Wed, Mar 26, 2025 at 1:36 PM Benno Lossin <benno.lossin@proton.me> wrote:
>> >> On Wed Mar 26, 2025 at 5:57 PM CET, Tamir Duberstein wrote:
>> >> >
>> >> > Yeah, we should do this - but again: not relevant in this discussion.
>> >>
>> >> I think it's pretty relevant.
>> >
>> > It's not relevant because we're no longer talking about transmuting
>> > pointer to pointer. The two options are:
>> > 1. transmute reference to reference.
>> > 2. coerce reference to pointer, `as` cast pointer to pointer (triggers
>> > `ptr_as_ptr`), reborrow pointer to reference.
>> >
>> > If anyone can help me understand why (2) is better than (1), I'd
>> > certainly appreciate it.
>>
>> I am very confident that (2) is correct. With (1) I'm not sure (see
>> above), so that's why I mentioned it.
>
> Can you help me understand why you're confident about (2) but not (1)?

My explanation from above explains why I'm not confident about (1):

For ptr-to-int transmutes, I know that they will probably remove
provenance, hence I am a bit cautious about using them for ptr-to-ptr or
ref-to-ref.

The reason I'm confident about (2) is that that is the canonical way to
cast the type of a reference pointing to an `!Sized` value.

---
Cheers,
Benno