src/test/ui/inference/cannot-infer-closure.rs - third_party/rust - Git at Google

 fn main() {
     let x = |a: (), b: ()| {
         Err(a)?; //~ ERROR type annotations needed for the closure
         Ok(b)
     };
 }
	fn main() {
	let x = \|a: (), b: ()\| {
	Err(a)?; //~ ERROR type annotations needed for the closure
	Ok(b)
	};
	}