// 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 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. // pretty-expanded FIXME #23616 pub trait NumCast: Sized { fn from(i: i32) -> Option; } pub trait NumExt: PartialEq + NumCast {} impl NumExt for f32 {} impl NumExt for isize {} impl NumCast for f32 { fn from(i: i32) -> Option { Some(i as f32) } } impl NumCast for isize { fn from(i: i32) -> Option { Some(i as isize) } } fn num_eq_one() -> T { NumCast::from(1).unwrap() } pub fn main() { num_eq_one::(); // you need to actually use the function to trigger the ICE }