print_err.rs

trait PrintError<E> {
    fn print_err(self, message: &'static str) -> Self;

    // The String type is allocated in the heap, so when a String is needed it's better to have a function that only allocates it in case it's necessary
    fn print_err_with<F>(self, message_f: F) -> Self
    where F: Fn(&E) -> String;
}

impl<T, E> PrintError<E> for Result<T, E> {
    fn print_err(self, message: &'static str) -> Result<T, E> {
        self.map_err(|err| {
            println!("{}", message);
            err
        })
    }

    fn print_err_with<F>(self, message_f: F) -> Result<T, E>
    where F: Fn(&E) -> String {
        self.map_err(|err| {
            println!("{}", message_f(&err));
            err
        })
    }
}