generic fibonacci in rust

fib.rs

extern crate num;

//use std::num::One;
use num::traits::One;
use std::cmp::PartialOrd;
use std::ops::{Add, Sub};

fn fib<T>(n: T) -> T where
  T: One + PartialOrd + Add<Output=T> + Sub<Output=T> + Clone {
    if n < T::one() + T::one() {
        n
    } else {
        fib(n.clone() - T::one() - T::one()) + fib(n.clone() - T::one())
    }
}

pub fn main() {
    println!("Hello, world!");
    println!("{}", fib(35));
}