#![warn(useless_format)] fn main() { format!("foo"); format!("{}", "foo"); format!("{:?}", "foo"); // we only want to warn about `{}` format!("{:+}", "foo"); // we only want to warn about `{}` format!("foo {}", "bar"); format!("{} bar", "foo"); let arg: String = "".to_owned(); format!("{}", arg); format!("{:?}", arg); // we only want to warn about `{}` format!("{:+}", arg); // we only want to warn about `{}` format!("foo {}", arg); format!("{} bar", arg); // we don’t want to warn for non-string args, see #697 format!("{}", 42); format!("{:?}", 42); format!("{:+}", 42); format!("foo {}", 42); format!("{} bar", 42); // we only want to warn about `format!` itself println!("foo"); println!("{}", "foo"); println!("foo {}", "foo"); println!("{}", 42); println!("foo {}", 42); }