Yeah, and I think this is the problem at the root of my gripe. If the committee was willing to reach this point earlier I think we’d be better off!
> But implementors are not: they can bless their own span with superpowers if they want to
Except that they don’t. And we can go around in circles here - I maintain this is a design issue, and it should be fixed at the design stage, rather than passed on to the compiler vendor who are stuck behind the theoretical design that pretends an ABI doesn’t exist, and their customers who will not upgrade if they break the ABI.
Lastly, I agree that the committee cannot force conformance or optimality, nor should they. But their unwillingness to accept that unless it’s technically impossible, the vendors will move mountains for conformance. This leaves us fighting with each other over who is to blame (see this thread), and in my opinion the end result is a half baked outcome that solves the paper problem but doesn’t solve the actual users wants.