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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/relate_tys/var-appears-twice.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/relate_tys/var-appears-twice.rs')
-rw-r--r-- | tests/ui/nll/relate_tys/var-appears-twice.rs | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/tests/ui/nll/relate_tys/var-appears-twice.rs b/tests/ui/nll/relate_tys/var-appears-twice.rs new file mode 100644 index 000000000..77129f446 --- /dev/null +++ b/tests/ui/nll/relate_tys/var-appears-twice.rs @@ -0,0 +1,25 @@ +// Test that the NLL `relate_tys` code correctly deduces that a +// function returning always its first argument can be upcast to one +// that returns either first or second argument. + +use std::cell::Cell; + +type DoubleCell<A> = Cell<(A, A)>; +type DoublePair<A> = (A, A); + +fn make_cell<'b>(x: &'b u32) -> Cell<(&'static u32, &'b u32)> { + panic!() +} + +fn main() { + let a: &'static u32 = &22; + let b = 44; + + // Here we get an error because `DoubleCell<_>` requires the same type + // on both parts of the `Cell`, and we can't have that. + let x: DoubleCell<_> = make_cell(&b); //~ ERROR + + // Here we do not get an error because `DoublePair<_>` permits + // variance on the lifetimes involved. + let y: DoublePair<_> = make_cell(&b).get(); +} |