Trying out the C# vNext `?.` operator in Sweet.js

null-guard.sjs

macro null_helper {
    rule { ($processed ...) ($rest) } => {
        $processed (.) ... . $rest
    }
    rule { ($processed ...) ($rest_head $rest ...) } => {
        $processed (.) ... . $rest_head
        && null_helper ($processed ... $rest_head) ($rest ...)
    }
}
 
macro (?.) {
    rule { ($x) } => {
        $x
    }
    rule infix { $head | $rest (.) ... } => {
        $head && null_helper ($head) ($rest ...)
    }
}

var x = {
	y: { z: { a: 42 } }
};

var foo = x?.y.z.a
console.log(foo);