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use std::marker::PhantomData;
trait DistributedIterator {
fn reduce(self)
where
Self: Sized,
{
unreachable!()
}
}
trait DistributedIteratorMulti<Source> {
type Item;
}
struct Connect<I>(PhantomData<fn(I)>);
impl<I: for<'a> DistributedIteratorMulti<&'a ()>> DistributedIterator for Connect<I> where {}
struct Cloned<Source>(PhantomData<fn(Source)>);
impl<'a, Source> DistributedIteratorMulti<&'a Source> for Cloned<&'a Source> {
type Item = ();
}
struct Map<I, F> {
i: I,
f: F,
}
impl<I: DistributedIteratorMulti<Source>, F, Source> DistributedIteratorMulti<Source> for Map<I, F>
where
F: A<<I as DistributedIteratorMulti<Source>>::Item>,
{
type Item = ();
}
trait A<B> {}
struct X;
impl A<()> for X {}
fn multi<I>(_reducer: I)
where
I: for<'a> DistributedIteratorMulti<&'a ()>,
{
DistributedIterator::reduce(Connect::<I>(PhantomData))
}
fn main() {
multi(Map { //~ ERROR implementation of `DistributedIteratorMulti` is not general enough
i: Cloned(PhantomData),
f: X,
});
}
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