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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:50 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:50 +0000 |
commit | 2e00214b3efbdfeefaa0fe9e8b8fd519de7adc35 (patch) | |
tree | d325add32978dbdc1db975a438b3a77d571b1ab8 /tests/ui/traits/new-solver/two-projection-param-candidates-are-ambiguous.rs | |
parent | Releasing progress-linux version 1.68.2+dfsg1-1~progress7.99u1. (diff) | |
download | rustc-2e00214b3efbdfeefaa0fe9e8b8fd519de7adc35.tar.xz rustc-2e00214b3efbdfeefaa0fe9e8b8fd519de7adc35.zip |
Merging upstream version 1.69.0+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'tests/ui/traits/new-solver/two-projection-param-candidates-are-ambiguous.rs')
-rw-r--r-- | tests/ui/traits/new-solver/two-projection-param-candidates-are-ambiguous.rs | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/tests/ui/traits/new-solver/two-projection-param-candidates-are-ambiguous.rs b/tests/ui/traits/new-solver/two-projection-param-candidates-are-ambiguous.rs new file mode 100644 index 000000000..cde2059ca --- /dev/null +++ b/tests/ui/traits/new-solver/two-projection-param-candidates-are-ambiguous.rs @@ -0,0 +1,30 @@ +// compile-flags: -Ztrait-solver=next + +// When we're solving `<T as Foo>::Assoc = i32`, we actually first solve +// `<T as Foo>::Assoc = _#1t`, then unify `_#1t` with `i32`. That goal +// with the inference variable is ambiguous when there are >1 param-env +// candidates. + +// We don't unify the RHS of a projection goal eagerly when solving, both +// for caching reasons and partly to make sure that we don't make the new +// trait solver smarter than it should be. + +// This is (as far as I can tell) a forwards-compatible decision, but if you +// make this test go from fail to pass, be sure you understand the implications! + +trait Foo { + type Assoc; +} + +trait Bar {} + +impl<T> Bar for T where T: Foo<Assoc = i32> {} + +fn needs_bar<T: Bar>() {} + +fn foo<T: Foo<Assoc = i32> + Foo<Assoc = u32>>() { + needs_bar::<T>(); + //~^ ERROR type annotations needed: cannot satisfy `T: Bar` +} + +fn main() {} |