rust pattern match rc

rbtree.rs

use std::rc::Rc;

#[derive(Clone, Debug, Eq, PartialEq)]
pub enum Color {
    Black,
    Red
}

use Color::{Black, Red};

#[derive(Clone, Debug, Eq, PartialEq)]
pub enum RedBlackTree<T> {
    Tip,
    Node(Color, Rc<RedBlackTree<T>>, T, Rc<RedBlackTree<T>>)
}

use RedBlackTree::{Tip, Node};

fn balance<T>(c: Color, l: Rc<RedBlackTree<T>>, v: T, r: Rc<RedBlackTree<T>>) -> RedBlackTree<T> {
    match (c, *l, v, *r) {
        (Black, Node(Red, Node(Red, a, x, b), y, c), z, d) |
        (Black, Node(Red, a, x, Node(Red, b, y, c)), z, d) |
        (Black, a, x, Node(Red, Node(Red, b, y, c), z, d)) |
        (Black, a, x, Node(Red, b, y, Node(Red, c, z, d))) =>
            Node(Red, Node(Black, a, x, b), y, Node(Black, c, z, d)),
        _ => Node(c, l, v, r)
        }
    }
}