src/test/ui/label/label-underscore.rs - third_party/rust - Git at Google

 fn main() {
     '_: loop { //~ ERROR invalid label name `'_`
         break '_ //~ ERROR invalid label name `'_`
     }
 }
	fn main() {
	'_: loop { //~ ERROR invalid label name `'_`
	break '_ //~ ERROR invalid label name `'_`
	}
	}