src/test/ui/transmutability/enums/should_order_correctly.rs


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32

// check-pass
//! The payloads of an enum variant should be ordered after its tag.

#![crate_type = "lib"]
#![feature(arbitrary_enum_discriminant)]
#![feature(transmutability)]
#![allow(dead_code)]

mod assert {
    use std::mem::BikeshedIntrinsicFrom;
    pub struct Context;

    pub fn is_transmutable<Src, Dst>()
    where
        Dst: BikeshedIntrinsicFrom<Src, Context, true, true, true, true>
    {}
}

#[repr(u8)] enum V0 { V = 0 }
#[repr(u8)] enum V1 { V = 1 }
#[repr(u8)] enum V2 { V = 2 }

#[repr(u8)] enum E01 { V0(V1) = 0u8 }
#[repr(u8)] enum E012 { V0(V1, V2) = 0u8 }

fn should_order_tag_and_fields_correctly() {
    // An implementation that (incorrectly) arranges E01 as [0x01, 0x00] will,
    // in principle, reject this transmutation.
    assert::is_transmutable::<E01, V0>();
    // Again, but with one more field.
    assert::is_transmutable::<E012, E01>();
}