List<int>? nullableList = [1, 2, 3];
Map<int, String>? nullableMap = {1: "Let", 2: "it", 3: "be"};
dynamic dynamicList = [1, 2, 3];
dynamic dynamicMap = {1: "Let", 2: "it", 3: "be"};
main() {}
testIterables<X extends dynamic, Y extends List<int>?, Z extends List<int>>(
    X x, Y y, Z z) {}
testMap<X extends dynamic, Y extends Map<int, String>?,
    Z extends Map<int, String>>(X x, Y y, Z z) {}
var i = 1;
var list1 = [
  if (i > 0) ...nullableList,
  if (i > 0) ...dynamicList,
  if (i > 0) ...nullableList!,
];
var map1 = {
  if (i > 0) ...nullableMap,
  if (i > 0) ...dynamicMap,
  if (i > 0) ...nullableMap!,
};
var set1 = {
  0,
  if (i > 0) ...nullableList,
  if (i > 0) ...dynamicList,
  if (i > 0) ...nullableList!
};