Optional bytemuck support

[edgarogh]

bytemuck allows safe transmuting of simple types with no uninhabited values. I would be really useful if hybrid-array implemented it the same way bytemuck implements it on native constant-sized arrays. Obviously, the dependency would be optional.

How ?

This is the impl for the standard generic array, it should be trivial to adapt:

unsafe impl<T, const N: usize> Pod for [T; N] where T: Pod {}

source: https://github.com/Lokathor/bytemuck/blob/005ee3254fdfa63d67d024cfc598319331dab0cb/src/pod.rs#L87

Why ?

• bytemuck is quite popular (3.5M downloads/month, 600+ GH stars)
• Implementing it would instantly make hybrid arrays of int/bytes/etc. safely transmutable with other kinds of arrays at no cost, including non-standard ones

Why not ?

• It adds a dependency
• It's always possible to get access to the underlying &[T; N]/&mut [T; N] (and vice-versa) using normal hybrid_array::Array methods and give these to bytemuck instead. It adds one "level" of conversion, which is acceptable.

[tarcieri]

I'd be okay with adding it as an optional dependency