bug#64442: 29.0.92; treesit-beginning-of-defun fails in DEFUN functions in C

[Yuan Fu]

> On Aug 12, 2023, at 7:59 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Thu, 10 Aug 2023 14:33:09 -0700
>> Cc: 64442@debbugs.gnu.org
>> 
>> I still don’t have a good solution. But I just realized that we might be 
>> able to make a little compromise: what if Emacs recognizes DEFUN, but as two 
>> separate parts (the declaration and the body), rather than one? It’s hard to 
>> make it recognize DEFUN as a single defun, but making it recognize DEFUN as 
>> two parts is easy.
>> 
>> Try this patch and see if you like the behavior. Personally I find it quite 
>> alright.
> 
> I like this much better than what we have now, thanks.  But I have a
> question: can we perhaps recognize the "function" of the body as such,
> and then automatically move to the previous defun, which is the right
> place?  The "defun" that is the body has no name, so maybe that could
> be used as a sign?  

We can easily tell the body from the declaration, but we can’t easily tell 
whether we should automatically move forward or backward. When point arrives at 
the point between the declaration and the body, should it move to the beginning 
of the next defun or the beginning of the declaration? This, plus it’s not 
straightforward to know whether we are in between a body and a declaration. I 
really don’t want to add even more cursed hacks into c-ts-mode.el :-)

> That would allow "C-x 4 a" to work inside a DEFUN,
> something that still works less reliably with this patch: you must be
> in the "first defun" to get it to find the name of the function.

C-x 4 a should’ve been fixed already. And it shouldn’t rely on this fix to 
work. Do you have a recipe for when it doesn’t work?

Yuan