Method heal_level

cranelift/bforest/src/path.rs:487–503

After removing an entry from the node at `level`, check its health and rebalance as needed. Leave the path up to and including `level` in a normalized state where all entries are in bounds. Returns true if the tree becomes empty.

(&mut self, status: Removed, level: usize, pool: &mut NodePool<F>)

    ///
    /// Returns true if the tree becomes empty.
    fn heal_level(&mut self, status: Removed, level: usize, pool: &mut NodePool<F>) -> bool {
        match status {
            Removed::Healthy => {}
            Removed::Rightmost => {
                // The rightmost entry was removed from the current node, so move the path so it
                // points at the first entry of the next node at this level.
                debug_assert_eq!(
                    usize::from(self.entry[level]),
                    pool[self.node[level]].entries()
                );
                self.next_node(level, pool);
            }
            Removed::Underflow => self.underflowed_node(level, pool),
            Removed::Empty => return self.empty_node(level, pool),
        }
        false
    }

    /// The current node at `level` has underflowed, meaning that it is below half capacity but
    /// not completely empty.