#![feature(plugin)] #![plugin(clippy)] #![deny(clippy)] #![allow(unused)] fn the_answer(ref mut x: u8) { //~ ERROR `ref` directly on a function argument is ignored *x = 42; } fn main() { let mut x = 0; the_answer(x); // Closures should not warn let y = |ref x| { println!("{:?}", x) }; y(1u8); println!("The answer is {}.", x); }