bug#60894: 30.0.50; [PATCH] Add treesit-forward-sexp

[Dmitry Gutov]

On 19/01/2023 05:58, Stefan Monnier via Bug reports for GNU Emacs, the 
Swiss army knife of text editors wrote:
> > > I think `C-M-u` from within a LaTeX environment was one of the cases
> > > where it misbehaved (tho that one is not using SMIE).
> > Any chance SMIE is doing something different, or something
> > particularly correct?
>
> Could be.  Maybe its simplistic approach rules out the bad cases?

Simplistic meaning one that uses a list of openers and closers?

> > > > Do you mean a hook like backward-up-list-function, or something smaller?
> > > Something like that.  Maybe it could also be used for `expand-region`
> > > and `thing-at-point` kind of purposes maybe and could work even for
> > > treesit nodes that aren't "matching begin..end thingies".
> > A treesit node doesn't need an explicit "end" token, though.
>
> And that's what I want: I want to use successive `C-M-u` (or
> `expand-region`) to consider ever greater subexpressions that include
> the position from which I started and to do that at a fine grain.
> E.g. if I start with point on `b` in:
>
>         a + b * c
>
> I'd like to first consider "b" then "b * c" then the whole thing.

That should be easy enough to do using the provided tree-sitter 
framework, just by adding binary nodes to the list of types.

Whether this behavior is preferable is a matter of opinion, though. My 
guess is Ruby users will find it too fiddly, and the end result is that 
one will have to press 'C-M-u' more times to get to the same result 
(which would usually be to get to the beginning of a block, or a 
method). But people can customize it.