javascript - sweet.js macro checking for null

gistfile1.js

macro null_helper {
    case ($processed ...) ($rest) => {
        $processed (.) ... . $rest
    }
    case ($processed ...) ($rest_head $rest ...) => {
        $processed (.) ... . $rest_head
        && null_helper ($processed ... $rest_head) ($rest ...)
    }
}

macro nullity {
    case ($x) => {
        $x
    }
    case ($head . $rest (.) ...) => {
        $head && null_helper ($head) ($rest ...)
    }
}

nullity (x.y.z)

// x && x.y && x.y.z