Comment by vlovich123

You don’t need to determine the internal representation as long as you’re dealing with opaque types and invoking rust functions on it.

As for the tricks used to make both 24 bytes, it’s NonNull within String that Option then detects and knows it can represent transparently without any enum tags. For what it’s worth you can do similar tricks in c++ using zero-sized types and tags to declare nullable state (in fact std::option already knows to do this for pointer types if I recall correctly)