What does an OClosure look like?

[Alan Mackenzie]

Hello, Emacs.

I'm currently experimenting with the layout of lambda forms.  In doing
so, I've hit a cl-assert in oclosure.el.

I can't find a description of an oclosure in that source file, nor in
the section in the elisp manual.  By description, I mean what an
oclosure structure looks like in terms of conses and lists.

Without such a description, I'll be reduced to the difficult process of
working this out for myself.  Difficult, because oclosure.el is largely
written in (to me) obscure cl- facilities, with which I am not familiar.

Could somebody (?Stefan, perhaps) point me at the description I need,
please.

Thanks!

-- 
Alan Mackenzie (Nuremberg, Germany).