tests/ui/lint/unused/unused-allocation.rs - rust-lang/rust - Git at Google

 #![deny(unused_allocation)]

 fn main() {
     _ = Box::new([1]).len(); //~ error: unnecessary allocation, use `&` instead
 }
	#![deny(unused_allocation)]

	fn main() {
	_ = Box::new([1]).len(); //~ error: unnecessary allocation, use `&` instead
	}