bug#53260: char-syntax differs in interpreter and bytecode

[Mattias Engdegård]

15 jan. 2022 kl. 15.46 skrev Stefan Monnier <monnier@iro.umontreal.ca>:

>    If you’re trying to determine the syntax of characters in the buffer,
>    this is probably the wrong function to use, because it can’t take
>    ‘syntax-table’ text properties into account.  Consider using
>    ‘syntax-after’ instead.
> 
> The "can't" is because `char-syntax` doesn't know where the char comes from.

This is true and it leaves a narrower use for `char-syntax` in mode-specific 
code -- ie, when syntax-table text properties do not need to be taken into 
account.

I propose we do the following:

1. Remove SETUP_BUFFER_SYNTAX_TABLE() from Fchar_syntax because as far as I can 
tell it has no effect at all.

2. Remove make_char_multibyte(c) from Bchar_syntax because it seems to be the 
wrong thing to do: in a unibyte buffer, wouldn't the syntax table be indexed by 
byte value (so that char 255 in the buffer corresponds to entry 255 in the 
syntax table rather than entry 0x3fffff)?

3. Now both implementations are identical. Replace the one in the byte-code 
interpreter with a call to Fchar_syntax.

> I think he meant "rare" w.r.t dynamic count rather than static count.

Yes, that's right.