Cannot use derive macros when reexporting bytemuck from library

[AndriBaal]

I have a crate that reexports bytemuck including its derive feature. I also have a derive macro that creates a new struct which should implement Pod and Zeroable. The problem I have is, that I cannot implement those traits on the struct using the safe derive macro because i get the following error:

error[E0433]: failed to resolve: could not find `bytemuck` in the list of imported crate

I assume this error occurs becuase the the crate uses ::bytemuck which always uses bytemuck as an extern crate dependency.

serde has a very elegant way to bypass this issue: serde-rs/serde#1465 (comment)

It would be nice to see something like this in the future, so that you can reexport bytemuck and still use the derive macros:

#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
#[bytemuck(crate = "self::bytemuck")]
#[repr(C)]
struct Test {
    position: InstancePosition,
    color: Color,
}

If the dev team would be interested in such a feature, I would be happy to make a pull request.

[Lokathor]

this appears to be the same problem as #93

I'd be happy to see some sort of fix here, but I'm not 100% sure that the fix you're proposing is the correct one. At a glance it seems fine. If you make the PR I can certainly point people at it to do the review.

[AndriBaal]

I have now implemented it in a similar way as serde #209

[cst0ny]

This issue should be closed as far as i can tell.

I cant find where this has been documented (CHANGELOG, docs.rs, etc...) but you can now do this in bytemuck 1.17 :
https://github.com/Lokathor/bytemuck/blob/main/derive/tests/basic.rs#L457

#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable, bytemuck::ByteEq)]
#[bytemuck(crate = "reexport_name")]
#[repr(C)]
struct Issue93 {}

[Lokathor]

I'll keep it open as a reminder to put this in docs somewhere, then we can close it.