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//check-pass
trait Yokeable<'a>: 'static {
type Output: 'a;
}
trait IsCovariant<'a> {}
struct Yoke<Y: for<'a> Yokeable<'a>> {
data: Y,
}
impl<Y: for<'a> Yokeable<'a>> Yoke<Y> {
fn project<Y2: for<'a> Yokeable<'a>>(&self, _f: for<'a> fn(<Y as Yokeable<'a>>::Output, &'a ())
-> <Y2 as Yokeable<'a>>::Output) -> Yoke<Y2> {
unimplemented!()
}
}
fn _upcast<Y>(x: Yoke<Y>) -> Yoke<Box<dyn IsCovariant<'static> + 'static>> where
Y: for<'a> Yokeable<'a>,
for<'a> <Y as Yokeable<'a>>::Output: IsCovariant<'a>
{
x.project(|data, _| {
Box::new(data)
})
}
impl<'a> Yokeable<'a> for Box<dyn IsCovariant<'static> + 'static> {
type Output = Box<dyn IsCovariant<'a> + 'a>;
}
fn main() {}
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