enum of traits

enum_of_traits.rs

#![feature(if_let)]
extern crate collections;
use collections::DList;
use collections::Deque;


trait Immut {
    fn immut_meth(&self);
}

trait Mut : Immut {
    fn mut_meth(&mut self);
}

struct Memory{
    d: uint
}

impl Immut for Memory {
    fn immut_meth(&self) {
        println!("Immut for memory");
    }
}

impl Mut for Memory {
    fn mut_meth(&mut self) {
        println!("Mut for Memory");
    }
}

struct Memwrp {
    d: int
}

impl Immut for Memwrp {
    fn immut_meth(&self) {  
        println!("Immut for Memwrp");
    }
}

enum DH{
    Mutable(Box<Mut + Send>),
    Immutable(Box<Immut + Send>)
}

fn foo(dl: &mut DList<DH>) {
    if let Some(ref mut dh) = dl.front_mut() {
        match dh {
            &&Mutable(ref mut m) => {
                m.mut_meth();
            }
            &&Immutable(ref im) => {
                im.immut_meth();
            }
        }
    }
    dl.pop_front();
}

fn main() {
    let mut dl = DList::new();
    dl.push(Mutable(box Memory{d:0}));
    dl.push(Immutable(box Memory{d:0}));
    dl.push(Immutable(box Memwrp{d:0}));
    foo(&mut dl); foo(&mut dl); foo(&mut dl);
}