The reason WTF-8 bytes are not exposed is not in case we change the internal representation later, it’s because anything one might do with them (except constructing another OsStr) is almost certainly wrong. WTF-8 is a hack that we made up for a very specific purpose. I’d be very sad if it accidentally becomes the de-facto encoding of some protocol because someone copied WTF-8 bytes from an OsStr into a file or a socket without realizing it’s not UTF-8. I’d very much prefer we don’t allow WTF-8 bytes to “leak” out of OsStr. (Though of course someone determined enough can always use transmute, but that’s less likely to be accidental.)
@kornel, what would you want to use this for?
As to encode_wide, what would it do on platforms where OsStr contains arbitrary bytes?