The simple approach would be to just use rgrep.

use M-xrgrep and specify searching for "function" in the current file in the current directory. You can wrap this up in a command so you don't have to specify the options each time.

This will yield a searchable buffer with the function signatures and you can jump to the definitions if you want.

The simple approach would be to just use rgrep.

use M-xrgrep and specify searching for "function" in the current file in the current directory. You can wrap this up in a command so you don't have to specify the options each time like this:

(defun rgrep-lua-functions ()
  "run `rgrep` searching for 'function' in the current file."
  (interactive)
  (rgrep "function" (file-name-nondirectory (buffer-file-name)) "."))

This will yield a searchable buffer with the function signatures and you can jump to the definitions if you want.