Let's continue discussion here: https://news.ycombinator.com/item?id=46416377

I think it's true that right up until 1.0, backtrace was a part of `trait Error`, then it was deprecated and removed, but there were ongoing discussions as late as 2021 about how the "point" of `std::backtrace::Backtrace` was to attach it to an `Error`. I have lots of links and references there.

As a user, that kind of meant that as long as I thought `trait Error` might grow backtraces someday, I should stay away from it in order to be friendly to embedded. And as long as it wasn't in core, that could still happen. I hope you can agree that it was far from clear what was going to happen until relatively recently.