@RalfJ i don't know what to do about the layout of unions, should I remove the unresolved question ?
I'd suggest say explicitly that this is about the ABI
but I think for now we dont want to make any guarantee for union ABI
maybe edit unions.md as well and add the question there?
seems like what we really want is
repr(transparent) for unions, this has all the same concerns
but someone should write an RFC if they want that guarantee :D
Yeah, I can move the question to the union's document, using vectors in ABI as an example. Something like repr(transparent) for unions sums this up nicely.