tests/ui/macros/bad_hello.rs - third_party/github.com/rust-lang/rust - Git at Google

 fn main() {
     println!(3 + 4);
     //~^ ERROR format argument must be a string literal
     println!(3, 4);
     //~^ ERROR format argument must be a string literal
 }
	fn main() {
	println!(3 + 4);
	//~^ ERROR format argument must be a string literal
	println!(3, 4);
	//~^ ERROR format argument must be a string literal
	}