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