private static bool IsSubset(ScalarEnumSet <T> a, ScalarEnumSet <T> b) => (a._elements & ~b._elements) == 0;
private static bool IsProperSubset(ScalarEnumSet <T> a, ScalarEnumSet <T> b) => IsSubset(a, b) && a.Count < b.Count;
public Enumerator(ScalarEnumSet <T> enumSet) { _enumSet = enumSet; }