Macro unwrap_or 

macro_rules! unwrap_or {
    ($opt:expr, $default:expr, $select:path) => { ... };
}

Helper macro for providing behavior like the CtOption::unwrap_or combinator that works in const fn contexts.

Requires a provided selector function $select to perform constant-time selection which takes two T values by reference along with a Choice, returning the first T for Choice::FALSE, and the second for Choice::TRUE, e.g.:

const fn ct_select(a: &T, b: &T, condition: Choice) -> T