Possibly incorrect Ord for SmallestCostHolder (in astar)

[glchapman]

Here is the code in question:

impl<K: Ord> Ord for SmallestCostHolder<K> {
    fn cmp(&self, other: &Self) -> Ordering {
        match other.estimated_cost.cmp(&self.estimated_cost) {
            Ordering::Equal => self.cost.cmp(&other.cost),
            s => s,
        }
    }
}

It seems to me that the inner cost comparison should be other.cost.cmp(&self.cost) preserving the sense (of the outer comparison) that if self has a lesser cost than other, cmp will produce Ordering::Greater (for the max heap).

[glchapman]

My apologies, this isn't really an issue. If two states have equal estimated_cost, then the only the only way one of them could have a lower cost is if it has a positive heuristic. Assuming an admissible heuristic (which never overestimates), this means the lower cost state cannot be a goal state, so it doesn't matter if it's produced after the higher cost state.