bug#22090: Isearch is sluggish and eventually refuses further service with "[Too many words]".

[Artur Malabarba <bruce.connor.am@gmail.com>]

2015-12-05 17:32 GMT+00:00 Eli Zaretskii <eliz@gnu.org>:
>> Because there are some characters in each regexp that don't have
>> lower/upper-case equivalents. For instance, if I use the
>> "\\(\\(a[´`]?\\|[áà𝑎]\\)" regexp, that's enough to match A or À, but
>> it's not enough to match a variety of other chars (𝔸𝕬𝖠𝗔𝘈𝘼𝙰🄰).
>
> You don't need to match the latter set.  Character folding is applied
> _after_ case folding, not before.  So characters that don't have a
> lower-case variant simply shouldn't match a lower-case a -- and they
> won't, if you just let case-insensitive regexp matching do its job.

Given that char-folding is a new feature, how it combines with
case-folding is entirely up to us, and I have really no idea what
would be TRT.
However, if that is your opinion, I'm more than happy to accept that
the current situation ('a' doesn't match '𝔸𝕬𝖠𝗔𝘈𝘼𝙰🄰') is TRT,
given that it has the simplest implementation. :-)