Allow `make_nested_status_code()` to consume `errored_status_code` instances

[BurningEnlightenment]

While adapting to ned14/status-code@c8b2779 I noticed that make_nested_status_code() rejects errored_status_code instances due to is_status_code<errored_status_code<...>>::value being false.

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It's also a bit unfortunate that OUTCOME_TRY can no longer convert rich llfio::file_io_error to system_error2::error due to ned14/status-code@c8b2779.

[ned14]

Fixed the first part.

Working on the second part, I have a repro. Thanks for discovering this regression.

[BurningEnlightenment]

Thanks for fixing the both issues. I wasn't sure whether the second part was intended or not, otherwise I would've opened a separate ticket.

[ned14]

The second issue its fix I think now actually works, it didn't work on older compilers.

Thanks for reporting it!

[ned14]

Can I undo how I implemented your second ask, which is the use of make_status_code() to enable implicit conversions between types of status code?

I had assumed that all bugs with recursive ADL had been fixed in recent compilers. But Apple's latest clang appears to be just as broken as an early C++ 11 compiler. And that's a major platform, so it's a bit of a showstopper.

I'll still fix the regression you originally reported, but I think I need to ban make_status_code() ever accepting a status code as input.

Thoughts? Also, Merry Christmas.

[BurningEnlightenment]

I'll still fix the regression you originally reported, but I think I need to ban make_status_code() ever accepting a status code as input.

Sure, I mean technically that should be a task for a constructor or conversion operator anyways. Previously we had that explicitly converting constructor which fulfilled the same function until it got prefixed with std::in_place_t. Given that you gave up on standardizing, we could revert this. Alternatively we could also teach outcome to use a std::in_place_t-prefixed converting constructor as a fallback option 🤔

In any case, Merry Christmas.

[ned14]

Ok, over the line and I made a release. Thanks for the BR!

[BurningEnlightenment]

I'll try to integrate the updated version tomorrow; thanks for the quick turnaround!