+ ((let ((file (directory-file-name
+ (nnmail-group-pathname group nnml-directory))))
+ (and (file-exists-p file)
+ (not (file-directory-p file))))
+ (nnheader-report 'nnml "%s is a file"
+ (directory-file-name
+ (let ((nnmail-pathname-coding-system nil))
+ (nnmail-group-pathname group nnml-directory)))))