Is there any built in way to “combine” two Options?

I don’t believe there’s a direct function equivalent to liftM2, but you can combine Option::and_then and Option::map like this:

fn main() {
    let a = Some(5);
    let b = Some(10);
    let f = |a, b| {
        a + b
    };

    println!("{:?}", a.and_then(|a| b.map(|b| f(a, b))));
}

Output:

Some(15)