Victor Zverovich wrote:
> The usual approach is to provide a char option (string_view in your case) that
> works properly in the common and the most important from the future
> evolution case of UTF-8 literal encoding. It would also be consistent with
> existing exceptions and the decision we made for P3068:
> https://github.com/cplusplus/papers/issues/1754#issuecomment-2299368606.
> You might want to elaborate why you can't optionally provide a
> u8 overload in addition to that.

If we base everything on string_view using the literal encoding, and
provide an additional u8string_view overload, we'll have to say what
happens when that u8 overload is given a string that is not representable
in the literal encoding.

In these cases, P2996 functions fail.

But we can't "fail" here, because throwing a meta::exception is precisely
how P2996 functions fail (as proposed in this paper).

See also section 2.1 of the paper,
https://isocpp.org/files/papers/P3560R0.html#encoding.

>
> Cheers,
> Victor
>
> On Sat, Jan 11, 2025 at 8:50 AM Barry Revzin via SG16 <sg16_at_[hidden]
> <mailto:sg16_at_[hidden]> > wrote:
>
>
> Hey all,
>
> Peter and I will have a paper in this upcoming mailing, which can be
> found here (https://isocpp.org/files/papers/P3560R0.html). We're proposing
> that error handling in reflection should use exceptions to be recoverable, now
> that it is possible to have recoverable exceptions during constant evaluation.
>
>
> The part that concerns this list is... what type should
> std::meta::exception::what() return: std::string_view or std::u8string_view?
>
>
>
> * Argument for u8string_view: this is the principled, type system
> correct answer.
> * Argument for string_view: this is the only type for which there is
> absolutely any support whatsoever in the standard library to do anything.
>
>
> As you all know, this is an area in which I have no expertise (neither
> current nor, if I'm being honest, desired). This discussion will have to go to
> SG16 eventually, so I wanted to just expedite the process.
>
> As we point out, P2996 used to originally use string_view everywhere
> and we changed to provide a dual interface (e.g. identifier_of() and
> u8identifier_of() both exist). That's not really feasible for std::meta::exception,
> we kind of have to pick one.
>
>
> Thanks,
>
>
> Barry
>
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