helpful-key throws wrong-type-arg error on closures

[shankar2k]

I'm having a error similar to one reported here, but for ordinary (non-byte-complied) closures.

Backtrace

Debugger entered--Lisp error: (wrong-type-argument symbolp (orig-fun . dired-next-line))
  symbol-name((orig-fun . dired-next-line))
  helpful--format-argument((orig-fun . dired-next-line))
  mapcar(helpful--format-argument ((orig-fun . dired-next-line) t))
  -map(helpful--format-argument ((orig-fun . dired-next-line) t))
  (cond (advertised-args (-map #'helpful--format-argument advertised-args)) ((listp function-args) (-map #'helpful--format-argument function-args)) (t (list function-args)))
  (let* ((function-args (cond ((symbolp sym) (help-function-arglist sym)) ((byte-code-function-p sym) (aref sym 0)) (t (cadr sym)))) (formatted-args (cond (advertised-args (-map #'helpful--format-argument advertised-args)) ((listp function-args) (-map #'helpful--format-argument function-args)) (t (list function-args))))) (setq source-sig (cond ((not (symbolp sym)) (format "(%s)" (s-join " " formatted-args))) (formatted-args (format "(%s %s)" (helpful--format-symbol sym) (s-join " " formatted-args))) (t (format "(%s)" (helpful--format-symbol sym))))))
  (let (docstring-sig source-sig (advertised-args (when (symbolp sym) (gethash (symbol-function sym) advertised-signature-table)))) (let* ((function-args (cond ((symbolp sym) (help-function-arglist sym)) ((byte-code-function-p sym) (aref sym 0)) (t (cadr sym)))) (formatted-args (cond (advertised-args (-map #'helpful--format-argument advertised-args)) ((listp function-args) (-map #'helpful--format-argument function-args)) (t (list function-args))))) (setq source-sig (cond ((not (symbolp sym)) (format "(%s)" (s-join " " formatted-args))) (formatted-args (format "(%s %s)" (helpful--format-symbol sym) (s-join " " formatted-args))) (t (format "(%s)" (helpful--format-symbol sym)))))) (-when-let (docstring (documentation sym)) (-when-let (docstring-with-usage (help-split-fundoc docstring sym)) (setq docstring-sig (car docstring-with-usage)))) (cond (advertised-args source-sig) (docstring-sig) (t source-sig)))
  helpful--signature((closure ((orig-fun . dired-next-line) t) (&optional arg) "Send a message before calling ORIG-FUN" (interactive "^p") (message "Foo is about to call %S" orig-fun) (call-interactively orig-fun)))
  helpful-update()
  helpful-key("\356")
  funcall-interactively(helpful-key "\356")
  call-interactively(helpful-key nil nil)
  command-execute(helpful-key)

Steps to Reproduce
Download the attached baz.el.txt to somewhere in your load-path and rename it to baz.el. Then run the following in Emacs:

(require 'helpful)
(require 'baz)
(dired ".")
(helpful-key (kbd "M-C"))

Potential Fix
I believe I was able to fix the problem with the following code modifications:

1. In helpful--in-manual-p, change line 1270 from:
   (assoc-string sym completions))))
   to:
   (and (stringp sym) (assoc-string sym completions)))))
2. In helpful--format-argument change line 2439 from
   (let ((arg-str (symbol-name arg)))
   to:
   (let ((arg-str (symbol-name (if (consp arg) (car arg) arg))))

I can provide this as a pull request if it would be more convenient.