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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /src/test/ui/nll/relate_tys/var-appears-twice.rs | |
parent | Initial commit. (diff) | |
download | rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip |
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/test/ui/nll/relate_tys/var-appears-twice.rs')
-rw-r--r-- | src/test/ui/nll/relate_tys/var-appears-twice.rs | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/src/test/ui/nll/relate_tys/var-appears-twice.rs b/src/test/ui/nll/relate_tys/var-appears-twice.rs new file mode 100644 index 000000000..77129f446 --- /dev/null +++ b/src/test/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(); +} |