module NullObject {
    void run() {
        @Inject Console console;
        console.print($"Null value={Null}, Null.toString()={Null.toString()}");

     // String s = Null;        // <-- compiler error: cannot assign Null to a String type
        String? s = Null;       // "String?" is shorthand for the union "Nullable|String"
        String s2 = "test";
        console.print($"{s=}, {s2=}, {s==s2=}");

     // Int len = s.size;       // <-- compiler error: String? does not have a "size" property
        Int len = s?.size : 0;
        console.print($"{len=}");

        if (String test ?= s) {
            // "s" is still Null in this test, we never get here
        } else {
            s = "a non-null value";
        }

     // if (String test ?= s){} // <-- compiler error: The expression type is not nullable
        s2 = s;                 // at this point, s is known to be a non-null String
        console.print($"{s=}, {s2=}, {s==s2=}");
    }
}