Hello,

I think I found a bug with `gnus-summary-refer-article'. If I fetch an
article that comes from another group, it gets inserted in the summary
with a number of -1. During the call to `gnus-summary-mark-article', the
following is done

(setq mark (gnus-request-update-mark gnus-newsgroup-name article mark))

which results in mark being nil. This in turn makes the comparisons such
as

(= mark gnus-unread-mark)

fail with a "Wrong type argument: number-or-marker-p, nil".

Here is a trimmed-down backtrace:

Debugger entered--Lisp error: (wrong-type-argument number-or-marker-p nil)
  =(nil 32)
  ...
  gnus-summary-mark-article(-1 82)
  gnus-summary-mark-read-and-unread-as-read()
  run-hooks(gnus-mark-article-hook)
  apply(run-hooks gnus-mark-article-hook)
  gnus-run-hooks(gnus-mark-article-hook)
  gnus-article-prepare(-1 nil)
  gnus-summary-display-article(-1 nil)
  gnus-summary-select-article(nil nil nil -1)
  (progn (gnus-summary-select-article nil nil nil number) (throw (quote found) t))
  ...
  gnus-summary-refer-article("52947012.308@cse.gu.se")
  call-interactively(gnus-summary-refer-article nil nil)
  command-execute(gnus-summary-refer-article)

Is this a known bug?

Thanks,

Alan

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