SG16 has an NB comment to deal with! Tom has already scheduled it for Belfast. It's basically that the list of allowed code points have some interesting control characters like zero width joiners and RTL modifiers.
https://github.com/cplusplus/nbballot/issues/28There's also an issue that JF raised earlier:
https://github.com/sg16-unicode/sg16/issues/48Improve support for Unicode characters in identifiers
Relevant unicode standard:
https://unicode.org/reports/tr31/ UNICODE IDENTIFIER AND PATTERN SYNTAX
Which is complicated because it allows things like identifiers written in Farsi which requires zwj for disambiguation, and suggests regex to detect particular allowed identifiers. It's fairly dense, and I haven't digested it yet, but it looks like there might be allowed ways to exclude that.
Plus tailoring would be needed because C++ disallows some characters such as '$' which might otherwise be allowed. This is also discussed in TR31.
My feeling on the comment is that it's not a new issue for C++20, so it's not clear that it has to be fixed for C++20. I believe it should be fixed, but it ought to be fixed in a principled manner, and that likely means TR31.
We would also have to discuss if emoji are allowed in identifiers. TR31 does not strictly disallow them. The TonyTable shall be interesting.
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