Macro Parameters

By default, all parameters are replaced literally when the macro is expanding. For example, if you pass an array literal to a macro, all uses of that parameter will be replaced with the EXACT array literal:

function $loop(arr: Array<number>, cb: (element: number) => void) {
    for (let i=0; i < arr.length; i++) {
        cb(arr[i]);
    }
}

$loop!([1, 2, 3, 4, 5], (el) => console.log(el)); 

for (let i = 0; i < [1, 2, 3, 4, 5].length; i++) {
    ((el) => console.log(el))([1, 2, 3, 4, 5][i]);
}

To avoid this, you can assign the literal to a variable, or use the Save marker.

function $loop(arr: Array<number>, cb: (element: number) => void) {
    const array = arr;
    for (let i=0; i < array.length; i++) {
        cb(array[i]);
    }
}

$loop!([1, 2, 3, 4, 5], (el) => console.log(el));

const array_1 = [1, 2, 3, 4, 5];
for (let i_1 = 0; i_1 < array_1.length; i_1++) {
    ((el) => console.log(el))(array_1[i_1]);
}