tests/ui/macros/auxiliary/issue-19163.rs - toolchain/rustc - Git at Google

 #![crate_type = "lib"]

 #[macro_export]
 macro_rules! mywrite {
     ($dst:expr, $($arg:tt)*) => ($dst.write_fmt(format_args!($($arg)*)))
 }
	#![crate_type = "lib"]

	#[macro_export]
	macro_rules! mywrite {
	($dst:expr, $($arg:tt)) => ($dst.write_fmt(format_args!($($arg))))
	}