Removing the first item in a Vec<T> is not difficult—in fact, Vec<T> ships with a swap_remove() function that does exactly what a heap needs: removing the first element of a Vec<T> by replacing it with the last element! This makes the code significantly shorter and therefore easier to reason about:
pub fn pop(&mut self) -> Option<MessageNotification> {
if self.length > 0 {
let elem = self.heap.swap_remove(0);
self.length = self.heap.len();
let mut i = 1;
while i * 2 < self.length {
let children = (i * 2, i * 2 + 1);
i = if self.has_more_messages(children.0, children.1) {
if self.has_more_messages(children.0, i) {
self.swap(i, children.0);
children.0
} else {
break;
}
} else {
if self.has_more_messages(children.1, i) {
self.swap...
