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1ad218f3af
As our implementation of MCP411 nears completion and we begin to solicit testing, it's no longer reasonable to expect testers to type or remember `BikeshedIntrinsicFrom`. The name degrades the ease-of-reading of documentation, and the overall experience of using compiler safe transmute. Tentatively, we'll instead adopt `TransmuteFrom`. This name seems to be the one most likely to be stabilized, after discussion on Zulip [1]. We may want to revisit the ordering of `Src` and `Dst` before stabilization, at which point we'd likely consider `TransmuteInto` or `Transmute`. [1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20should.20.60BikeshedIntrinsicFrom.60.20be.20named.3F
37 lines
1.0 KiB
Rust
37 lines
1.0 KiB
Rust
//! The target endianness should be a consideration in computing the layout of
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//! an enum with a multi-byte tag.
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#![crate_type = "lib"]
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#![feature(transmutability)]
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#![allow(dead_code)]
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mod assert {
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use std::mem::{Assume, TransmuteFrom};
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pub fn is_transmutable<Src, Dst>()
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where
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Dst: TransmuteFrom<Src, {
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Assume::ALIGNMENT
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.and(Assume::LIFETIMES)
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.and(Assume::SAFETY)
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.and(Assume::VALIDITY)
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}>
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{}
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}
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#[repr(u16)] enum Src { V = 0xCAFE }
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#[repr(u8)] enum OxCA { V = 0xCA }
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#[repr(u8)] enum OxFE { V = 0xFE }
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#[cfg(target_endian = "big")] #[repr(C)] struct Expected(OxCA, OxFE);
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#[cfg(target_endian = "big")] #[repr(C)] struct Unexpected(OxFE, OxCA);
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#[cfg(target_endian = "little")] #[repr(C)] struct Expected(OxFE, OxCA);
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#[cfg(target_endian = "little")] #[repr(C)] struct Unexpected(OxCA, OxFE);
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fn should_respect_endianness() {
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assert::is_transmutable::<Src, Expected>();
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assert::is_transmutable::<Src, Unexpected>(); //~ ERROR cannot be safely transmuted
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}
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