>> On Thu, 30 Oct 2014 14:21:34 +0900
>> yamaoka@jpl.org (Katsumi Yamaoka) said as follows:

>> However, Gnus failed to open the IMAP server.  Its error message is:

>>     Unable to open server nnimap+imap.example.net due to: Wrong type
>>     argument: listp, #<process *nnimap*>

>> I used edebug to investigate the cause of this trouble, and found
>> that open-network-stream() is called wihtout `parameters' argument.

>Have you edebugged open-protocol-stream (proto-stream.el)?
>nnimap uses it instead, and it calls open-network-stream without
>`parameters' on some condition.

In my environment, Emacs 24.3 on Debian GNU/Linux,
open-protocol-stream() is defined as follows:

    (defalias 'open-protocol-stream 'open-network-stream)

in /usr/share/emacs/24.3/lisp/net/network-stream.el.
There is a conflict between two function definitions, maybe.

I explicitly load proto-stream.el distributed with Gnus, and tried
re-connection.  After that, Gnus's error message changed into:

    Warning: Unable to open server nnimap+imap.example.net due to: Wrong
    type argument: stringp, nil

It is able to suppress this error by the attached patch because
`capabilities' is equal to nil, however, I cannot enter any IMAP group.
I think that the attached patch is not right solution and my trouble may
be caused by the other origin.

-- 
TSUCHIYA Masatoshi