rust/src/test/run-pass/trait-inheritance-num5.rs

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use cmp::{Eq, Ord};
use num::Num::from_int;

pub trait NumExt: Eq Num {}

pub impl f32: NumExt {}
pub impl int: NumExt {}

fn num_eq_one<T:NumExt>() -> T {
    from_int(1)
}

fn main() {
    num_eq_one::<int>(); // you need to actually use the function to trigger the ICE
}