I see that #711 was closed by #771. I agree with the proposed resolution not to put the Zone ID in the IPv6 address type -- it is indeed not part of of an IPv6 address. However, I think that just putting it in url_view url_view_base and not url, authority_view, etc. means that the work is not yet finished --- some operations support Zone IDs and others do not, and it can be tricky to figure out either case.

See for example the hack that my NixOS/nix#13819 will do to get around this.

In particular, the issue is that url_view::host_address and url::set_host_address do not round-trip as expected in the presence of Zone IDs.