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use std::marker::PhantomData;
pub trait StatefulFuture<S> {}
pub struct Never<T>(PhantomData<T>);
impl<T> StatefulFuture<T> for Never<T> {}
pub struct RaceBuilder<F, S> {
future: F,
_phantom: PhantomData<S>,
}
impl<T, F> RaceBuilder<T, F>
where
F: StatefulFuture<Option<T>>,
{
pub fn when(self) {}
}
pub struct Race<T, R> {
race: R,
_phantom: PhantomData<T>,
}
impl<T, R> Race<T, R>
where
R: Fn(RaceBuilder<T, Never<T>>),
{
pub fn new(race: R) {}
}
fn main() {
Race::new(|race| race.when()); //~ ERROR type annotations needed
}
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