This is a flag object that does not behave as I meant it to:
```
enum E
{
   OptionA,
   OptionB,
   OptionC,
   OptionD
}
Flags!E f;
assert(!(f & E.OptionA)); // fails
f |= E.OptionD;
assert(!(f & E.OptionB)); // fails
assert(!(f & E.OptionC)); // fails
```