[rustc.git] / src / test / ui / transmutability / enums / should_order_correctly.rs

// check-pass
//! The payloads of an enum variant should be ordered after its 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(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>();
}
Commit	Line	Data
064997fb FG	1	// check-pass
	2	//! The payloads of an enum variant should be ordered after its tag.
	3
	4	#![crate_type = "lib"]
064997fb FG	5	#![feature(transmutability)]
	6	#![allow(dead_code)]
	7
	8	mod assert {
f2b60f7d	9	use std::mem::{Assume, BikeshedIntrinsicFrom};
064997fb FG	10	pub struct Context;
	11
	12	pub fn is_transmutable<Src, Dst>()
	13	where
f2b60f7d FG	14	Dst: BikeshedIntrinsicFrom<Src, Context, {
	15	Assume::ALIGNMENT
	16	.and(Assume::LIFETIMES)
	17	.and(Assume::SAFETY)
	18	.and(Assume::VALIDITY)
	19	}>
064997fb FG	20	{}
	21	}
	22
	23	#[repr(u8)] enum V0 { V = 0 }
	24	#[repr(u8)] enum V1 { V = 1 }
	25	#[repr(u8)] enum V2 { V = 2 }
	26
	27	#[repr(u8)] enum E01 { V0(V1) = 0u8 }
	28	#[repr(u8)] enum E012 { V0(V1, V2) = 0u8 }
	29
	30	fn should_order_tag_and_fields_correctly() {
	31	// An implementation that (incorrectly) arranges E01 as [0x01, 0x00] will,
	32	// in principle, reject this transmutation.
	33	assert::is_transmutable::<E01, V0>();
	34	// Again, but with one more field.
	35	assert::is_transmutable::<E012, E01>();
	36	}