diff options
Diffstat (limited to 'tests/ui/traits/new-solver/leak-check-coinductive-cycle.rs')
-rw-r--r-- | tests/ui/traits/new-solver/leak-check-coinductive-cycle.rs | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/tests/ui/traits/new-solver/leak-check-coinductive-cycle.rs b/tests/ui/traits/new-solver/leak-check-coinductive-cycle.rs new file mode 100644 index 000000000..1f7d4a49c --- /dev/null +++ b/tests/ui/traits/new-solver/leak-check-coinductive-cycle.rs @@ -0,0 +1,33 @@ +// check-pass +// compile-flags: -Ztrait-solver=next +#![feature(rustc_attrs)] + +#[rustc_coinductive] +trait Trait<T> {} +impl<'a, 'b, T> Trait<T> for (&'a (), &'b ()) +where + 'b: 'a, + &'a (): Trait<T>, +{} + +impl Trait<i32> for &'static () {} +impl<'a> Trait<u32> for &'a () +where + for<'b> (&'a (), &'b ()): Trait<u32>, +{} + + +fn impls_trait<T: Trait<U>, U>() {} + +fn main() { + // This infers to `impls_trait::<(&'static (), &'static ()), i32>();` + // + // In the first attempt we have 2 candidates for `&'a (): Trait<_>` + // and we get ambiguity. The result is therefore ambiguity with a `'b: 'a` + // constraint. The next attempt then uses that provisional result when + // trying to apply `impl<'a> Trait<u32> for &'a ()`. This means we get a + // `for<'b> 'b: 'a` bound which fails the leak check. Because of this we + // end up with a single impl for `&'a (): Trait<_>` which infers `_` to `i32` + // and succeeds. + impls_trait::<(&(), &()), _>(); +} |