VariantN opAssign(T)(T rhs)
Assigns a VariantN from a generic argument. Statically rejects disallowed types.
VariantN
VariantN opAssign(T : VariantN!(tsize, Types), size_t tsize, Types...)(T rhs) if (!is(T : VariantN) && Types.length > 0 && allSatisfy!(allowed, Types))