rust/src/test/ui/feature-gate-macro_at_most_once_rep.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.

// Test that `?` macro Kleene operator can not be used when the `macro_at_most_once_rep` feature
// gate is not used.

macro_rules! m { ($(a)?) => {} }
//~^ ERROR Using the `?` macro Kleene operator for "at most one" repetition is unstable

fn main() {
    m!();
}