error: useless use of `format!` --> format.rs:6:5 | 6 | format!("foo"); | ^^^^^^^^^^^^^^^ | = note: `-D useless-format` implied by `-D warnings` error: useless use of `format!` --> format.rs:8:5 | 8 | format!("{}", "foo"); | ^^^^^^^^^^^^^^^^^^^^^ error: useless use of `format!` --> format.rs:15:5 | 15 | format!("{}", arg); | ^^^^^^^^^^^^^^^^^^^ error: aborting due to 3 previous errors To learn more, run the command again with --verbose.