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[rustc.git] / src / test / ui / transmutability / structs / should_order_fields_correctly.rs
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FG
1// check-pass
2//! The fields of a struct should be laid out in lexical order.
3
4#![crate_type = "lib"]
5#![feature(transmutability)]
6#![allow(dead_code)]
7
8mod assert {
f2b60f7d 9 use std::mem::{Assume, BikeshedIntrinsicFrom};
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FG
10 pub struct Context;
11
12 pub fn is_transmutable<Src, Dst>()
13 where
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FG
14 Dst: BikeshedIntrinsicFrom<Src, Context, {
15 Assume::ALIGNMENT
16 .and(Assume::LIFETIMES)
17 .and(Assume::SAFETY)
18 .and(Assume::VALIDITY)
19 }>
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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(C)] struct S01(V0, V1);
28#[repr(C)] struct S012(V0, V1, V2);
29
30fn should_order_tag_and_fields_correctly() {
31 // An implementation that (incorrectly) arranges S01 as [0x01, 0x00] will,
32 // in principle, reject this transmutation.
33 assert::is_transmutable::<S01, V0>();
34 // Again, but with one more field.
35 assert::is_transmutable::<S012, S01>();
36}