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//! The variants of an enum must be padded with uninit bytes such that they have
//! the same length (in bytes).
#![crate_type = "lib"]
#![feature(transmutability)]
#![allow(dead_code)]
mod assert {
use std::mem::{Assume, BikeshedIntrinsicFrom};
pub fn is_transmutable<Src, Dst, Context>()
where
Dst: BikeshedIntrinsicFrom<Src, Context, {
Assume::ALIGNMENT
.and(Assume::LIFETIMES)
.and(Assume::SAFETY)
.and(Assume::VALIDITY)
}>
{}
}
#[derive(Clone, Copy)]
#[repr(C)] struct Zst;
#[derive(Clone, Copy)]
#[repr(u8)] enum V0 { V = 0 }
#[derive(Clone, Copy)]
#[repr(u8)] enum V2 { V = 2 }
#[repr(C, u8)]
enum Lopsided {
Smol(Zst),
Lorg(V0),
}
#[repr(C)] struct Src(V0, Zst, V2);
#[repr(C)] struct Dst(Lopsided, V2);
fn should_pad_variants() {
struct Context;
// If the implementation (incorrectly) fails to pad `Lopsided::Smol` with
// an uninitialized byte, this transmutation might be (wrongly) accepted:
assert::is_transmutable::<Src, Dst, Context>(); //~ ERROR cannot be safely transmuted
}
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