Re-pushing with the highest priority does not always put the item in the top

[da-x]

The following example re-pushes "d" with the highest priority among all already pushed items. We expect to see "d" as the first time in .pop(), but we see "a" instead, and "d" comes second.

extern crate priority_queue;

use priority_queue::PriorityQueue;

fn main() {
    let mut pq : PriorityQueue<&'static str, usize> = PriorityQueue::new();

    pq.push("a", 9);
    pq.push("b", 8);
    pq.push("c", 7);
    pq.push("d", 6);

    // Re-pushing with the highest priority
    pq.push("d", 20);

    let mut prev_opt = None;
    for (item, x) in pq.into_sorted_iter() {
        println!("{:?} {:?}", item, x);
        if let Some(prev) = prev_opt {
            if prev < x {
                println!("WTF");
            }
        }
        prev_opt = Some(x);
    }
}

Output:

"a" 9
"d" 20
WTF
"b" 8
"c" 7

Tested along with:

[dependencies]
priority-queue = { git = "https://github.com/garro95/priority-queue" }

[da-x]

I think change_priority also needs a fix for this bug.

Thanks.

[garro95]

Done