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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:13 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:13 +0000 |
commit | 218caa410aa38c29984be31a5229b9fa717560ee (patch) | |
tree | c54bd55eeb6e4c508940a30e94c0032fbd45d677 /tests/ui/nll/issue-54556-niconii.rs | |
parent | Releasing progress-linux version 1.67.1+dfsg1-1~progress7.99u1. (diff) | |
download | rustc-218caa410aa38c29984be31a5229b9fa717560ee.tar.xz rustc-218caa410aa38c29984be31a5229b9fa717560ee.zip |
Merging upstream version 1.68.2+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'tests/ui/nll/issue-54556-niconii.rs')
-rw-r--r-- | tests/ui/nll/issue-54556-niconii.rs | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/tests/ui/nll/issue-54556-niconii.rs b/tests/ui/nll/issue-54556-niconii.rs new file mode 100644 index 000000000..cae389e8c --- /dev/null +++ b/tests/ui/nll/issue-54556-niconii.rs @@ -0,0 +1,31 @@ +// This is a reduction of a concrete test illustrating a case that was +// annoying to Rust developer niconii (see comment thread on #21114). +// +// With resolving issue #54556, pnkfelix hopes that the new diagnostic +// output produced by NLL helps to *explain* the semantic significance +// of temp drop order, and thus why inserting a semi-colon after the +// `if let` expression in `main` works. + +struct Mutex; +struct MutexGuard<'a>(&'a Mutex); + +impl Drop for Mutex { fn drop(&mut self) { println!("Mutex::drop"); } } +impl<'a> Drop for MutexGuard<'a> { fn drop(&mut self) { println!("MutexGuard::drop"); } } + +impl Mutex { + fn lock(&self) -> Result<MutexGuard, ()> { Ok(MutexGuard(self)) } +} + +fn main() { + let counter = Mutex; + + if let Ok(_) = counter.lock() { } //~ ERROR does not live long enough + + // With this code as written, the dynamic semantics here implies + // that `Mutex::drop` for `counter` runs *before* + // `MutexGuard::drop`, which would be unsound since `MutexGuard` + // still has a reference to `counter`. + // + // The goal of #54556 is to explain that within a compiler + // diagnostic. +} |