Rollup merge of #129032 - jswrenn:transmute-method, r=compiler-errors · patricklam/verify-rust-std@932cbd4 (original) (raw)

Rollup merge of rust-lang#129032 - jswrenn:transmute-method, r=compiler-errors

Document & implement the transmutation modeled by `BikeshedIntrinsicFrom` Documents that `BikeshedIntrinsicFrom` models transmute-via-union, which is slightly more expressive than the transmute-via-cast implemented by `transmute_copy`. Additionally, we provide an implementation of transmute-via-union as a method on the `BikeshedIntrinsicFrom` trait with additional documentation on the boundary between trait invariants and caller obligations. Whether or not transmute-via-union is the right kind of transmute to model remains up for discussion [1]. Regardless, it seems wise to document the present behavior. [1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20'kind'.20of.20transmute.20to.20model.3F/near/426331967Tracking Issue: rust-lang#99571r? `@compiler-errors` cc `@scottmcm,` `@Lokathor`