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//@ check-fail
//! Reject extensions behind references.
#![crate_type = "lib"]
#![feature(transmutability)]
mod assert {
use std::mem::{Assume, TransmuteFrom};
pub fn is_transmutable<Src, Dst>()
where
Dst: TransmuteFrom<
Src,
{
Assume {
alignment: true,
lifetimes: true,
safety: true,
validity: true,
}
},
>,
{
}
}
#[repr(C, packed)]
struct Packed<T>(T);
fn reject_extension() {
#[repr(C, align(2))]
struct Two(u8);
#[repr(C, align(4))]
struct Four(u8);
// These two types differ in the number of trailing padding bytes they have.
type Src = Packed<Two>;
type Dst = Packed<Four>;
const _: () = {
use std::mem::size_of;
assert!(size_of::<Src>() == 2);
assert!(size_of::<Dst>() == 4);
};
assert::is_transmutable::<&Src, &Dst>(); //~ ERROR cannot be safely transmuted
}
|
