tests/ui/box/alloc-unstable-fail.rs - rust-lang/rust - Git at Google

 use std::boxed::Box;

 fn main() {
     let _boxed: Box<u32, _> = Box::new(10);
     //~^ ERROR use of unstable library feature `allocator_api`
 }
	use std::boxed::Box;

	fn main() {
	let _boxed: Box<u32, _> = Box::new(10);
	//~^ ERROR use of unstable library feature `allocator_api`
	}