bug#71777: 29.4; sexp-at-point in latex-mode when sexp contains "; "

[Eli Zaretskii]

> Date: Tue, 25 Jun 2024 19:53:59 +0200
> From: Gabriele Nicolardi <gabriele@medialab.sissa.it>
> 
> I have this string expression in latex-mode:
> 
> $K(U_1, V_1, x_1; t_2, x_2)$
> 
> If the pointer is located on the opened "(" and I run "forward-sexp" it 
> works and the
> pointer goes after the closed ")".
> 
> But if, again, the pointer is located on the opened "(" and I evaluate
> "(sexp-at-point)" it returns nil.
> 
> If I remove the ";" symbol from the expression it works and returns the 
> sexp-at-point:
> 
> $K(U_1, V_1, x_1 t_2, x_2)$
> 
> Is it a bug?

I don't think it's a bug.  forward-sexp moves across balanced
expressions, so it is not specific to Lisp.  By contrast,
sexp-at-point is specific to Lisp and Lisp-like syntax, and so it uses
the buffer's syntax.  Which is why ';' affects the result.

Adding Stefan in case he has comments for this.