Re: Patch: make eldoc indicate current argument

[Stefan Monnier <monnier@iro.umontreal.ca>]

>     I was aware of such things (optional parameters in brackets), but
>     didn't figure out what to do with them:

> 	;; FIXME: What to do with optional arguments, like in
> 	;;        (defun NAME ARGLIST [DOCSTRING] BODY...) case?
> 	;;        The problem is there is no robust way to determine if
> 	;;        the current argument is indeed a docstring.

> Doc strings are so important that eldoc may as well have special-case
> code for them.

Hmm.... I'm trying to figure out in which circumstance it would be useful or
even possible to distinguish the two args in the help info:

- if point is on the second sexp (or further) in the body, it obviously
  won't make any difference.
- so it only makes a potential difference if point is on the first sexp in
  the body.
- if we don't do anything special, this will always be listed as being on
  [DOCSTRING].
- so if we're looking at a string, this is right unless there's
  no sexp afterwards.
- if we're looking at nothing, then selecting [DOCSTRING] is as good
  as any.
- if we're looking at an open paren an open [, then this is wrong,
  although only marginally so: we're just *before* the BODY and the user may
  decide to insert a docstring at point, so showing [DOCSTRING] isn't such
  a bad idea after all.
- we're inside a number or a symbol: this case is indeed just wrong and the
  help data should indicate we're in the BODY part.


-- Stefan