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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:06:37 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:06:37 +0000 |
commit | 246f239d9f40f633160f0c18f87a20922d4e77bb (patch) | |
tree | 5a88572663584b3d4d28e5a20e10abab1be40884 /src/test/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs | |
parent | Releasing progress-linux version 1.64.0+dfsg1-1~progress7.99u1. (diff) | |
download | rustc-246f239d9f40f633160f0c18f87a20922d4e77bb.tar.xz rustc-246f239d9f40f633160f0c18f87a20922d4e77bb.zip |
Merging debian version 1.65.0+dfsg1-2.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/test/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs')
-rw-r--r-- | src/test/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/src/test/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs b/src/test/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs new file mode 100644 index 000000000..9b9e4496a --- /dev/null +++ b/src/test/ui/higher-rank-trait-bounds/hrtb-exists-forall-trait-invariant.rs @@ -0,0 +1,29 @@ +// Test an `exists<'a> { forall<'b> { 'a = 'b } }` pattern -- which should not compile! +// +// In particular, we test this pattern in trait solving, where it is not connected +// to any part of the source code. + +use std::cell::Cell; + +trait Trait<T> {} + +fn foo<T>() +where + T: Trait<for<'b> fn(Cell<&'b u32>)>, +{ +} + +impl<'a> Trait<fn(Cell<&'a u32>)> for () {} + +fn main() { + // Here, proving that `(): Trait<for<'b> fn(&'b u32)>` uses the impl: + // + // - The impl provides the clause `forall<'a> { (): Trait<fn(&'a u32)> }` + // - We instantiate `'a` existentially to get `(): Trait<fn(&?a u32)>` + // - We unify `fn(&?a u32)` with `for<'b> fn(&'b u32)` + // - This requires (among other things) instantiating `'b` universally, + // yielding `fn(&!b u32)`, in a fresh universe U1 + // - So we get `?a = !b` but the universe U0 assigned to `?a` cannot name `!b`. + + foo::<()>(); //~ ERROR implementation of `Trait` is not general enough +} |