From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- src/test/ui/nll/relate_tys/var-appears-twice.rs | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) create mode 100644 src/test/ui/nll/relate_tys/var-appears-twice.rs (limited to 'src/test/ui/nll/relate_tys/var-appears-twice.rs') 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 = Cell<(A, A)>; +type DoublePair = (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(); +} -- cgit v1.2.3