Streaming Iterators in a Trait

streaming_iter.rs

trait HasIter<'a, T> {
  type IterType: Iterator<Item = T>;
}

trait Collection<T>: for<'a> HasIter<'a, &'a T> {
  fn iter<'a>(&'a self) -> <Self as HasIter<'a, &'a T>>::IterType;
}

struct Bar<T>(T);
struct BarIter<'a, T>(&'a Bar<T>);

impl<'a, T> Iterator for BarIter<'a, T> {
    type Item = &'a T;

    fn next(&mut self) -> Option<&'a T> {
        Some(&(self.0).0)
    }
}

impl<'a, T> HasIter<'a, &'a T> for Bar<T> {
    type IterType = BarIter<'a, T>;
}

impl<T> Collection<T> for Bar<T> {
    fn iter<'a>(&'a self) -> BarIter<'a, T> {
        BarIter(self)
    }
}