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// compile-flags: -Ztrait-solver=next
// check that when computing `alias-eq(<() as Foo<u16, T>>::Assoc, <() as Foo<?0, T>>::Assoc)`
// we do not infer `?0 = u8` via the `for<STOP> (): Foo<u8, STOP>` impl or `?0 = u16` by
// relating substs as either could be a valid solution.
trait Foo<T, STOP> {
type Assoc;
}
impl<STOP> Foo<u8, STOP> for ()
where
(): Foo<u16, STOP>,
{
type Assoc = <() as Foo<u16, STOP>>::Assoc;
}
impl Foo<u16, i8> for () {
type Assoc = u8;
}
impl Foo<u16, i16> for () {
type Assoc = u16;
}
fn output<T, U>() -> <() as Foo<T, U>>::Assoc
where
(): Foo<T, U>,
{
todo!()
}
fn incomplete<T>()
where
(): Foo<u16, T>,
{
// `<() as Foo<u16, STOP>>::Assoc == <() as Foo<_, STOP>>::Assoc`
let _: <() as Foo<u16, T>>::Assoc = output::<_, T>();
//~^ error: type annotations needed
// let _: <() as Foo<u16, T>>::Assoc = output::<u8, T>(); // OK
// let _: <() as Foo<u16, T>>::Assoc = output::<u16, T>(); // OK
}
fn main() {}
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