Deriving Pod for arbitrary generic types - Githubissues

Lokathor / bytemuck

A crate for mucking around with piles of bytes

https://docs.rs/bytemuck

Apache License 2.0

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Deriving Pod for arbitrary generic types #222

Open reinerp opened 7 months ago

reinerp commented 7 months ago

If we were willing to break backwards compatibility, it would be possible to support deriving Pod for arbitrary generic types.

The approach:

extend trait Pod to include const POST_MONOMORPHISM_CHECKS_PASS: bool;
the derive(Pod) instance puts its checks inside this POST_MONOMORPHISM_CHECKS_PASS constant. Since this is a trait member, it is allowed to reference the generic types.
(the backwards incompatible part) require that any function that uses T: Pod to do some form of safe transmute of T must first do assert!(POST_MONOMORPHISM_CHECKS_PASS);.

Lokathor commented 7 months ago

We might do this some day for version 2 (but that's far far in the future).