An attempt at a List that has the length encoded as a type parameter in Rust using phantom types. I wasn't able to get list_zip to compile unfortunately.

list.rs

use std::cast::transmute;

struct Zero;
struct Succ<T>;
struct Prev<T>;

enum List<T,N> {
  Nil,
  Cons (T, ~List<T,N>)
}

fn nil<T> () -> ~List<T, Zero> { ~Nil }
fn cons<T,N> (hd: T, tl: ~List<T,N>) -> ~List<T,Succ<N>> {
  unsafe { transmute(~Cons (hd, tl)) }
}

fn singleton<T>(t: T) -> ~List<T,Succ<Zero>> {
  cons (t, nil ())
}
/*
fn list_zip<A,B,N> (xs: ~List<A,N>, ys: ~List<B,N>) -> ~List<(A,B),N> {
  match (xs, ys) {
    (~Nil, ~Nil) => { nil () }
    (~Cons (x, xs), ~Cons (y,ys)) => { cons((x,y), list_zip(xs, ys)) }
  }
}
i*/
fn print_list<T,N>(xs: ~List<T,N>) {
  match *xs {
    Nil => { () }
    Cons (x, xs) => { 
      println(fmt!("%?", x));
      print_list(xs);
    } 
  }
}

fn main() {
  let a = singleton(5);
  let b = cons (1, cons (2, a));
  print_list(b);
}