Invalid custom dependency `temporary-file-directory'

[Lennart Borgman]

When I wrote

  :set-after 'temporary-file-directory

in a defcustom I got the error message above. I am unfortunately not 
very fond of it ;-)  -- I suggest instead something like

 "Custom dependency should be a list"

in this case. The information in "(elisp) Variable Definitions" could 
more explicitly state that VARIABLES means a list of variables for the 
:set-after keyword.