Document decoded-time-string issue on 6-elt args

* lisp/simple.el: Document problematic use of decoded-time-dst on
6-element args.

diff --git a/lisp/simple.el b/lisp/simple.el
index a254ee225144e2436e84e7999ac0862d255dc14a..d6b70454324bca6142499d0e1d1fdf2a783a1eac 100644 (file)
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -10519,6 +10519,14 @@ This is an integer indicating the UTC offset in seconds, i.e.,
 the number of seconds east of Greenwich.")
   )
 
+;; Document that decoded-time-dst is problematic on 6-element lists.
+;; It should return -1 indicating unknown DST, but currently returns
+;; nil indicating standard time.
+(put 'decoded-time-dst 'function-documentation
+     (append (get 'decoded-time-dst 'function-documentation)
+             "As a special case, `decoded-time-dst' returns an unspecified
+value when given a list too short to have a dst element."))
+
 (defun get-scratch-buffer-create ()
   "Return the *scratch* buffer, creating a new one if needed."
   (or (get-buffer "*scratch*")