Re: Plug treesit.el into other emacs constructs

[Eli Zaretskii]

> From: Yuan Fu <casouri@gmail.com>
> Date: Wed, 14 Dec 2022 16:05:10 -0800
> Cc: Theodor Thornhill <theo@thornhill.no>,
>  emacs-devel <emacs-devel@gnu.org>,
>  eliz@gnu.org
> 
> > I see, so maybe sexp means the general, flexible AST entity. And thinking 
> > of it, my idea is just forward-list :-) And we definitely should include 
> > forward-list into the list of navigation commands we want to support, among 
> > the ones that are already brought up.
> 
> Ok, upon closer inspection, forward-list isn’t exactly what I’m thinking 
> about, it moves over lists, but I’m thinking about moving over elements of a 
> list.
> 
> If you think about it, there are two kinds of constructs in an AST/grammar: 
> those are repeatable, and those are not. Statements are repeatable, you can 
> stack multiple ones together and it still makes sense. Identifiers are not 
> repeatable, put two together doesn’t make sense (in most languages).
> 
> And these repeatable constructs appears at every level of the AST, from 
> top-level stuff like function definition, to statements, to small stuff like 
> arguments in an argument list. That makes them very good unit of navigation.
> 
> Navigation commands, IMO, needs to be extremely easy to predict and requires 
> no thinking. That’s the reason why avy never grow on me: yes you can move to 
> anywhere you want, but it takes so much cognitive load to use. Much better to 
> type a few C-n, C-M-f, etc to get their, because I don’t need to think about 
> it.

FWIW, for me, "sexp" in its C/C++ interpretation always means
"expression".  So in

   foobar (a, b + c, 2 * d - f / 10 + pow (g, x), y);

C-M-f should move to the next comma on the top level (i.e. the comma
inside the 'pow' call doesn't count), and C-M-f inside the 'pow' call
should move by commas on that level.

More generally, C-M-f should move to the next expression
_on_the_same_level_, without entering inner levels.  Exactly like we
do in Lisp.