int sum(int[]? arr) {
    var z = 0;
    if?(int[] a = arr) {
      for(var i = 0; i<length(a); i = i + 1;) {
        z = z + a[i];
      }
    }
    return z;
}

int program (int argc, string[] argv) {
    var x = 0;
    x = x + sum(new int[]{1,2,3});
    x = x + sum(int[] null);
    return x;
}