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-rw-r--r--tests/ui/issues/issue-49298.rs42
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diff --git a/tests/ui/issues/issue-49298.rs b/tests/ui/issues/issue-49298.rs
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+// 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
+
+// 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>());
+}