src/test/ui/feature-gates/feature-gate-box_patterns.rs - third_party/rust - Git at Google

 fn main() {
     let box x = Box::new('c'); //~ ERROR box pattern syntax is experimental
     println!("x: {}", x);
 }
	fn main() {
	let box x = Box::new('c'); //~ ERROR box pattern syntax is experimental
	println!("x: {}", x);
	}