Redundant to_string?

[smoelius]

I was surprised that there does not seem to be a lint to catch the following. Is it possible that it exists and I am somehow not triggering it?

use camino::Utf8PathBuf;

fn main() {
    let path = Utf8PathBuf::from("src/main.rs");
    println!("{}", path.to_string()); // to_string is unnecessary since Utf8PathBuf implements Display
    println!("{}", path);
}

[camsteffen]

Related to #7667, and probably should be implemented together. I'd call this to_string_in_format_args.

[akanalytics]

Is it true that
a) println!("{:<20}", struct.to_string());
gives the same result as
b) println!("{:<20}", struct);

?

Doesnt it depend on how the formatter is written.
Line a) uses the default "{}" display to render a string then renders the string using the formatting rules :<20
Whereas b) uses the formatting rules of the struct's display, not the string's display trait impl.

But clippy seems to still flag this.

[camsteffen]

@akanalytics Feel free to file a bug if you found a false positive.