implement for &[T] and &mut [T]

[Stebalien]

Implementing for references over arbitrary unsized types doesn't work because it may not be safe to cast between them (I think?). But it's definitely safe to do this for [T].

This makes it possible to perform casts like cast!(some_slice, &[u8]) (useful for optimizing for byte arrays).

[sagebind]

Nice addition! You're right, this seems to be sound from my assessment and could be a really useful feature. Thanks for the PR!

[sagebind]

Implementing for references over arbitrary unsized types doesn't work because it may not be safe to cast between them (I think?).

The main problem with unsized types is that it becomes more difficult to statically verify that two types are equal. We have checks on the size and alignment because TypeId can have collisions in rare scenarios, but we can't use those safeguards on unsized types.

Aside from that, it would be safe to cast a type where T: ?Sized + 'static. Perhaps it could be something we could support in the future more generally -- it could be added without breaking compatibility with this PR.

[sagebind]

This has been published in version 0.1.2.

[Stebalien]

Aside from that, it would be safe to cast a type where T: ?Sized + 'static. Perhaps it could be something we could support in the future more generally -- it could be added without breaking compatibility with this PR.

That exceeds my rust-fu for now, unfortunately.