34 lines
971 B
Rust
34 lines
971 B
Rust
// compile-flags: -Znext-solver
|
|
// check-pass
|
|
#![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::<(&(), &()), _>();
|
|
}
|