fn cmp(&self, other: &Self) -> Ordering {
        assert!(ptr::eq(self.1, other.1));
        let ord = self.0.cmp(&other.0);
        if self.1.flipped.get() { ord.reverse() } else { ord }
    }
Descends to the nearest node where the edge matching the lower bound
of the range is different from the edge matching the upper bound, i.e.,
the nearest node that has at least one key contained in the range.

If found, returns an `Ok`
benchmarks/haystacks/code/rust-library.rs