#![feature(nll)]

use std::collections::HashMap;

struct Node {
    children: HashMap<String, Option<Box<Node>>>,
}

fn main() {
    let mut node = Node::new("xyz");

    // cur_node was in another function and pointed to root of tree.
    let mut cur_node = &mut node;

    // I wanted to traverse the nodes.
    // So, The if block in this gets a immutable reference to node
    // The code in else tries to get a mutable reference and update the node.
    // but it doesn't works! because cur_node.children.get() has a mutable reference and there can only be one mutable reference.
    if let Some(node) = cur_node.children.get_mut("abc") {
        cur_node = node.as_mut().unwrap();
    } else {
        // Create folder
        let n = Box::new(Node::new("abc"));

        // This does not works. It returns as_mut not found on &Node
        cur_node.children.insert("abc".into(), Some(n));
    }
}

impl Node {
    fn new(name: &str) -> Node {
        let mut h = HashMap::new();
        h.insert(name.to_owned(), None);
        Node { children: h }
    }
}