IPAddr#ipv4_compat

# File tmp/rubies/ruby-3.1.3/lib/ipaddr.rb, line 329
def ipv4_compat
  warn "IPAddr\##{__callee__} is obsolete", uplevel: 1 if $VERBOSE
  if !ipv4?
    raise InvalidAddressError, "not an IPv4 address: #{@addr}"
  end
  return self.clone.set(@addr, Socket::AF_INET6)
end