[Bug libstdc++/71500] regex::icase only works on first character in a range

[mwd at md5i dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71500

--- Comment #11 from Michael Duggan <mwd at md5i dot com> ---
"timshen at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> writes:

> (In reply to Michael Duggan from comment #9)
>> I will make two suggestions.  The initial suggestion is simple enough:
>> Given that regex_traits is mandated to be implemented by the library for
>> char and wchar_t, it would be reasonable, I think, to make the
>> specializations that handled these that go ahead and use the locale.
>> This falls into the "as if" rule, where an implementation is fine as
>> long as it works "as if" the more correct way was implemented.
>
>> The other suggestion is this.  Given that the more correct is "terribly
>> inefficient and impractical", I posit that you have three options: Use
>> the "correct", but "bad", implementation, leave the "incorrect in all
>> cases" implementation in place, or just go ahead and use the locale to
>> implement toggle_case().  Of these three, I think the "incorrect in all
>> cases" option is the worst of all worlds.
>
> In long term I think "toggle_case" or its equivalent should be specified by the
> user-defined traits. I think we can use my toggle_case for now. I'll post a new
> patch to reflect the discussion.
>
> I'll only post the patch after we have an agreement, since I shouldn't bother
> the reviewer (sorry Jon!) too frequently. :P

Sounds good to me.