There's a barrier to setting up the diagnostic pattern. When you're in the greenfield phase it's easy to search for information about error reporting, discover various different approaches and long threads of people arguing about what better and just say "ah screw it, I have more important things to do right now" and postpone the decision.
Your approach is fine, I don't love how verbose it is but it could probably be tweaked. If this is the way forward then it should be included in stdlib, documented, and promoted as the recommended way of reporting errors.
