Correct it.

use std::sync::Arc;
use std::rc::Rc;
use std::fmt::Debug;
use std::cell::RefCell;

#[derive(Debug, PartialEq, Clone, Copy)]
enum NodeType{
    Node,
    Leaf
}
#[derive(Debug)]
struct Node<K, V> {
    node_type: NodeType,
    keys: Vec<K>,
    values: Option<Vec<V>>,
    children: Option<Vec<Rc<RefCell<Node<K, V>>>>>,
    next: Option<Rc<RefCell<Node<K, V>>>>
}

pub fn upper_bound2<K: Ord + Debug + Clone>(keys: &[K], key: &K) -> usize {
    let mut index: i32 = -1;
    for i in 0..keys.len(){
        let ref k = keys[i];
        if *key < *k { index = i as i32; break; }
    }
    if index == -1{ index = keys.len() as i32; }
    return index as usize;
}

fn choose_subtree_mut<'a, K: Ord + Debug + Clone, V: Debug + Clone>(node: &'a mut Node<K,V>,k: &K) ->&'a mut Node<K, V> {
    match node.node_type {
        NodeType::Leaf => { return node; }
        NodeType::Node => {
            let index = upper_bound2(&node.keys, &k);
            println!("Child index: {:?}", index);
            match node.children {
                Some(ref mut node) => choose_subtree_mut(&mut node[index].borrow_mut(),k),
                None => panic!(""),
            }
        }
    }
}
fn main() {
    
}