"Wrong type argument" with latest emacs-snapshot

[Lele Gaifax <lele@metapensiero.it>]

Hi all,

today a friend asked me some help, since while trying to install Emacs
on a new Debian "sid" machine, he got some wierd error when
bootstrapping my own variation of the popular starter-kit setup.

Effectively, after upgrading my own machine from emacs-snapshot
2:20130603 to 2:20130618, I was able to replicate the problem, narrowing
the setup to the following ~/.emacs:

    (require 'package)
    (add-to-list 'package-archives
                 '("melpa" . "http://melpa.milkbox.net/packages/") t)
    (add-to-list 'package-archives
                 '("marmalade" . "http://marmalade-repo.org/packages/") t)
    (package-initialize)

    (defvar packages (list 'auto-complete 'darcsum))

    (defun install-packages ()
      (interactive)
      (dolist (package packages)
        (unless (or (member package package-activated-list)
                    (functionp package))
          (message "Installing %s" (symbol-name package))
          (package-install package))))

    (install-packages)

which while working perfectly with the previous version, triggers the
following error with the latest version:

    Wrong type argument: arrayp, auto-complete

I tried using the "--debug-init" option, as well as digging a little
with the elisp debugger, but I was not able to understand what is going
wrong with the new version: as soon as I reach (and execute) the
following lines of the `package-install` function I get the error

  (package-download-transaction
   ;; FIXME: Use (list pkg-desc) instead of just the name.
   (package-compute-transaction (list (package-desc-name pkg-desc))
                                (package-desc-reqs pkg-desc))))


If I install the packages interactively with M-x package-install
everything works as expected, and Emacs starts up without errors with
the setup above.

Do you have any hint about the possible reason for the reported error?

Thanks a lot in advance,
bye, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele@metapensiero.it  |                 -- Fortunato Depero, 1929.