master 7f7acf3956 3/3: Document decoded-time-string issue on 6-elt args

[Paul Eggert]

branch: master
commit 7f7acf395697e4cfa470cfa2993b70c2308e95c1
Author: Paul Eggert <eggert@cs.ucla.edu>
Commit: Paul Eggert <eggert@cs.ucla.edu>

    Document decoded-time-string issue on 6-elt args
    
    * lisp/simple.el: Document problematic use of decoded-time-dst on
    6-element args.
---
 lisp/simple.el | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lisp/simple.el b/lisp/simple.el
index a254ee2251..d6b7045432 100644
--- 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*")