// Copyright 2018 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. #![feature(decl_macro)] macro modern($a: ident) { struct Modern { a: u8, $a: u8, // OK } } macro_rules! legacy { ($a: ident) => { struct Legacy { a: u8, $a: u8, //~ ERROR field `a` is already declared } } } modern!(a); legacy!(a); fn main() {}