rust/tests/ui/transmutability/enums/should_respect_endianness.rs

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//! The target endianness should be a consideration in computing the layout of
//! an enum with a multi-byte tag.
#![crate_type = "lib"]
#![feature(transmutability)]
#![allow(dead_code)]
mod assert {
use std::mem::{Assume, BikeshedIntrinsicFrom};
pub struct Context;
pub fn is_transmutable<Src, Dst>()
where
Dst: BikeshedIntrinsicFrom<Src, Context, {
Assume::ALIGNMENT
.and(Assume::LIFETIMES)
.and(Assume::SAFETY)
.and(Assume::VALIDITY)
}>
{}
}
#[repr(u16)] enum Src { V = 0xCAFE }
#[repr(u8)] enum OxCA { V = 0xCA }
#[repr(u8)] enum OxFE { V = 0xFE }
#[cfg(target_endian = "big")] #[repr(C)] struct Expected(OxCA, OxFE);
#[cfg(target_endian = "big")] #[repr(C)] struct Unexpected(OxFE, OxCA);
#[cfg(target_endian = "little")] #[repr(C)] struct Expected(OxFE, OxCA);
#[cfg(target_endian = "little")] #[repr(C)] struct Unexpected(OxCA, OxFE);
fn should_respect_endianness() {
assert::is_transmutable::<Src, Expected>();
assert::is_transmutable::<Src, Unexpected>(); //~ ERROR cannot be safely transmuted
}