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#![feature(never_type)]
#![feature(transmutability)]
use std::mem::{Assume, TransmuteFrom};
pub fn is_transmutable<Src, Dst>()
where
Dst: TransmuteFrom<Src, { Assume::SAFETY }>,
{
}
fn main() {
is_transmutable::<char, u32>();
// `char`s can be in the following ranges:
// - [0, 0xD7FF]
// - [0xE000, 10FFFF]
//
// `Char` has variants whose tags are in the top and bottom of each range.
// It also has generic variants which are out of bounds of these ranges, but
// are generic on types which may be set to `!` to "disable" them in the
// transmutability analysis.
#[repr(u32)]
enum Char<B, C, D> {
A = 0,
B = 0xD7FF,
OverB(B) = 0xD800,
UnderC(C) = 0xDFFF,
C = 0xE000,
D = 0x10FFFF,
OverD(D) = 0x110000,
}
is_transmutable::<Char<!, !, !>, char>();
is_transmutable::<Char<(), !, !>, char>();
//~^ ERROR cannot be safely transmuted into `char`
is_transmutable::<Char<!, (), !>, char>();
//~^ ERROR cannot be safely transmuted into `char`
is_transmutable::<Char<!, !, ()>, char>();
//~^ ERROR cannot be safely transmuted into `char`
}
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