What it does

Warn when a Debug representation of Path is used in format! or println!, instead of path.display().

Advantage

Rust doesn't guarantee how Debug formatting looks like, and it could change in the future. For printing paths there's the dedicated .display() method.

Drawbacks

Not every Debug print of a Path is incorrect: it may be used in dbg!(), or when a PathBuf is a field in a struct that is Debug-printed as a whole.

Example

let path = Path::new("…");
println!("The path is {:?}", path);

Could be written as:

let path = Path::new("…");
println!("The path is {}", path.display());