Returning default value from function when result is error

Question

Is there something similar to the ? shortcut which instead of returning a result from a function when there is an error, returns a predefined value?

Basical

Answer 1

There is no such utility, but you can always write a macro:

macro_rules! return_if_err {
    ( $to_test:expr, $default:expr ) => (
        if $to_test.is_err() {
            return $default;
        }
    )
}

fn pop_or_default(mut v: Vec) -> i32 {
    let result = v.pop();
    return_if_err!(result.ok_or(()), 123);

    result.unwrap()
}

fn main() {
    assert_eq!(pop_or_default(vec![]), 123);
}

You cannot return from an outer scope from a closure.