Bug report: B c nnfolder:foo doesn't work

[Matt Armstrong <matt@lickey.com>]

I have these settings, which may be relevant to this bug:

(setq gnus-select-method '(nnml ""))
(setq gnus-secondary-select-methods '((nntp "news.speakeasy.net")))

So, my primary select method is nnml and most e-mail is stored in nnml
groups.  I am using yesterday's CVS.

Today, for the heck of it, I decided to create a nnfolder group to
store some e-mail with good ideas in it.  So I did:

      B c

And entered "nnfolder:ideas" as the group name and Gnus says it saved
it off okay.  What follows was screwy:

  - The Mail/ideas and Mail/ideas.nov file were created correctly, as
    was an entry in the Mail/active file: "ideas 1 1 y".

  - In addition, an empty file Mail/archive/ideas was created, as was
    a Mail/archive/ideas.mrk file.  Mail/archive/active contains
    "ideas 0 1 y".

  - The following three entries are placed in gnus-newsrc-alist:
  
    ("ideas" 3 nil nil)
    ("nnfolder+archive:ideas" 3 nil nil
     (nnfolder "archive"
	       (nnfolder-directory "~/g/Mail/archive")
	       (nnfolder-active-file
		"~/g/Mail/archive/active")
	       (nnfolder-get-new-mail nil)
	       (nnfolder-inhibit-expiry t)))
    ("nnfolder:ideas" 3 nil nil "archive")


When I exit and re-load Gnus, I get:

Signaling: (file-error "Opening output file" "not a directory" "/home/matt/g/Mail/ideas/.marks")
  write-region(1 10 "/home/matt/g/Mail/ideas/.marks" nil 0)
  byte-code(<snip>)
  nnml-save-marks("ideas" "")
  nnml-open-marks("ideas" "")
  nnml-request-update-info("ideas" ("ideas" 3 nil nil) "")
  gnus-get-unread-articles(nil)
  gnus-setup-news(nil nil nil)
  byte-code(<snip>)
  gnus-1(nil nil nil)
  gnus()
  (if buffer (switch-to-buffer buffer) (gnus))
  (let ((buffer ...)) (if buffer (switch-to-buffer buffer) (gnus)))
  my-goto-gnus()
  call-interactively(my-goto-gnus)

In addition, the "ideas" folder doesn't show up with an nnfolder:
prefix in the group list.

Clearly, the fact that this is an nnfolder group and not an nnml group
got lost at some point.

Please let me know if I can help debug this any further!

-- 
matt