Copy of a test from libcore/iterator.rs that somehow can't compile.

RegionBug

use core::iterator::UnfoldrIterator;

fn test_unfoldr() {
    fn count(st: &mut uint) -> Option<uint> {
        if *st < 10 {
            let ret = Some(*st);
            *st += 1;
            ret
        } else {
            None
        }
    }

    let mut it = UnfoldrIterator::new(count, 0);
    let mut i = 0;
    for it.advance |counted| {
        assert_eq!(counted, i);
        i += 1;
    }
    assert_eq!(i, 10);
}

fn main() {}