Enhancing font-locking in emacs-lisp-mode

[Nordlöw]

Hi again!

Some thoughts regarding enhancements of font-locking in emacs-lisp-
mode; I believe the readability of emacs-lisp code would be greatly
enhanced by also highlighting the following cases

- arguments to function/macro definition (defun/defmacro) in font-lock-
variable-name-face
- local variable names defined by the let/let* statement
- function name part of function calls: I guess this is hard/
(impossible?) to get right for all cases but maybe we could somehow
reuse `functionp' in the MATCHER to better filter out the more
relevant cases?

Does anyone have any tips on how to go about implementing this. For
the second case I believe I have to use a function matcher in font-
lock-keywords that navigates in the sub-expression structure (forward/
backward-sexp, backward-up-list, down-list). I now know how regexp-
MATCHERs work. Does anyone have any good tutorial on how to design
these function-MATCHERS?

Is it adviced to solve this as an add-on or is it best to let the GNU
Emacs hackers add this functionality to lisp-mode.el?

/Nordlöw