| //@ run-pass | |
| #![feature(test)] | |
| #![allow(unused_mut)] // under NLL we get warning about `x` below: rust-lang/rust#54499 | |
| // This test is bogus (i.e., should be check-fail) during the period | |
| // where #54986 is implemented and #54987 is *not* implemented. For | |
| // now: just ignore it | |
| // | |
| //@ ignore-test (#54987) | |
| // This test is checking that the space allocated for `x.1` does not | |
| // overlap with `y`. (The reason why such a thing happened at one | |
| // point was because `x.0: Void` and thus the whole type of `x` was | |
| // uninhabited, and so the compiler thought it was safe to use the | |
| // space of `x.1` to hold `y`.) | |
| // | |
| // That's a fine thing to test when this code is accepted by the | |
| // compiler, and this code is being transcribed accordingly into | |
| // the ui test issue-21232-partial-init-and-use.rs | |
| extern crate test; | |
| enum Void {} | |
| fn main() { | |
| let mut x: (Void, usize); | |
| let mut y = 42; | |
| x.1 = 13; | |
| // Make sure `y` stays on the stack. | |
| test::black_box(&mut y); | |
| // Check that the write to `x.1` did not overwrite `y`. | |
| // Note that this doesn't fail with optimizations enabled, | |
| // because we can't keep `x.1` on the stack, like we can `y`, | |
| // as we can't borrow partially initialized variables. | |
| assert_eq!(y.to_string(), "42"); | |
| // Check that `(Void, usize)` has space for the `usize` field. | |
| assert_eq!(std::mem::size_of::<(Void, usize)>(), | |
| std::mem::size_of::<usize>()); | |
| } |