#![feature(tool_lints)] #![allow(clippy::print_literal)] #![warn(clippy::useless_format)] struct Foo(pub String); macro_rules! foo { ($($t:tt)*) => (Foo(format!($($t)*))) } fn main() { format!("foo"); format!("{}", "foo"); format!("{:?}", "foo"); // don't warn about debug format!("{:8}", "foo"); format!("{:width$}", "foo", width = 8); format!("{:+}", "foo"); // warn when the format makes no difference format!("{:<}", "foo"); // warn when the format makes no difference format!("foo {}", "bar"); format!("{} bar", "foo"); let arg: String = "".to_owned(); format!("{}", arg); format!("{:?}", arg); // don't warn about debug format!("{:8}", arg); format!("{:width$}", arg, width = 8); format!("{:+}", arg); // warn when the format makes no difference format!("{:<}", arg); // warn when the format makes no difference 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); // A format! inside a macro should not trigger a warning foo!("should not warn"); // precision on string means slicing without panicking on size: format!("{:.1}", "foo"); // could be "foo"[..1] format!("{:.10}", "foo"); // could not be "foo"[..10] format!("{:.prec$}", "foo", prec = 1); format!("{:.prec$}", "foo", prec = 10); format!("{}", 42.to_string()); let x = std::path::PathBuf::from("/bar/foo/qux"); format!("{}", x.display().to_string()); }