[m-rev.] for post-commit review: propagate type char into insts

[Zoltan Somogyi]

2021-06-08 15:21 GMT+10:00 "Julien Fischer" <jfischer at opturion.com>:
> That test could be stronger, for example:
> 
>     :- inst key_char for char/0
>         --->    ('s')
>         ;       b
>         ;       0'a
>         ;       0'Δ
>         ;       ('\n').

I would not want to add any code using the 0' notation inherited
from Prolog. Since I wish it would go die in a fire :-(, I don't want to
even hint that this syntax is something we encourage.

> (I'm not sure if the fouth one is something we actually support
> or something that just happens to work.)
> 
> You should add an entry to the NEWS file saying that insts for chars
> are now supported.

Those two paragraphs contradict each other :-(

Until someone who knows Unicode very well (maybe Peter, definitely
not me) has checked the whole mode analysis pass without finding
any places where we mishandle non-ASCII chars, I would not want
to make such an announcement. At the moment, I don't think I would
even want to claim we support insts containing only ASCII chars
until we have much more experience with this diff ourselves.

I do thank you for the review.

Zoltan.