More TransparentWrapper impls (core::cmp::Reverse and core::num::Saturating)

[zachs18]

core::num::Saturating<T> is #[repr(transparent)] and was stabilized in Rust 1.74.0, so a new cargo feature is added transparentwrapper_extra to hold this and other TransparentWrapper impls for types stabilized after Rust 1.34.0.

core::cmp::Reverse<T> was stabilized in Rust 1.19.0, but only gained #[repr(transparent)] in Rust 1.52.0, so it is also under the transparentwrapper_extra feature¹.

cc #21

Footnotes

1. This ensures soundness, since there is no case where feature = "transparentwrapper_extra" compiles on a Rust version where Reverse is not #[repr(transparent)]. Any version of Rust will either: 1. have both stable Saturating and #[repr(transparent)] Reverse (1.74.0 and above), 2. not compile bytemuck with the transparentwrapper_extra feature because Saturating is not stable (below 1.74.0). ↩

[Lokathor]

released in bytemuck-1.20