rust/src/test/ui/span/macro-span-replacement.rs

// Copyright 2017 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.

#![warn(unused)]

macro_rules! m {
    ($a:tt $b:tt) => {
        $b $a; //~ WARN struct is never used
    }
}

fn main() {
    m!(S struct);
}