bug#81611: 31.0.90; show-paren-mode reports false mismatch

>> > Suggested fix: Before narrowing, check syntax-ppss at the cutoff; if it
>> > is inside a string or comment, don't cut there -- but snap forward (or
>> > backward) to a position outside strings/comments.
>> 
>> +1
>> 
>> And I believe the "snap forward" can be done by `parse-partial-sexp` with
>> COMMENTSTOP arg of `syntax-table`.  The snap backward is simpler (just
>> jump to (nth 8 ppss)), but could jump very far back if the
>> string/comment is very long.
>
> Wouldn't syntax-ppss run the risk of going far back?

Of course, but if it does, it's presumably to the benefit of all other
users of `syntax-ppss`, such as the backward-sexp call we'll do to find
the opening paren.  Also, in practice, font-lock should have caused
`syntax-ppss` to be updated at least until point, so it should be
"cheap" to compute at (- (point) blink-matching-paren-distance).


=== Stefan