Function fallible_once_err 

pub fn fallible_once_err<L: ?Sized + CovariantFallibleLending, E>(
    error: E,
) -> OnceErr<L, E>

Creates a fallible lender that yields a single error.

This is the error counterpart to once(): it yields one error and then returns Ok(None).

Examples

let mut lender = lender::fallible_once_err::<
    fallible_lend!(&'lend i32), _,
>("error".to_string());
assert_eq!(lender.next(), Err("error".to_string()));
assert_eq!(lender.next(), Ok(None));