#![feature(plugin)] #![plugin(clippy)] #![deny(string_add_assign)] #![deny(string_add)] fn main() { let mut x = "".to_owned(); for _ in (1..3) { x = x + "."; //~ERROR you assign the result of adding something to this string. } let y = "".to_owned(); let z = y + "..."; //~ERROR you add something to a string. assert_eq!(&x, &z); }