read-key-sequence(-vector) on Shift left/right gives [left]/[right], not [S-left]/[S-right] ?

["Drew Adams" <drew.adams@oracle.com>]

(defun foo ()
 (interactive)
 (let ((foo (read-key-sequence-vector "" )))
 (message "foo: %s" foo)))

Execute foo, press Shift+[left] or Shift+[right]. The message ([left] or
[right]) shows that the Shift modifier is lost.

However, if you press Shift+[up] or Shift+[down], the message is [S-up] or
[S-down]. That seems correct to me.

Same thing with read-key-sequence as with read-key-sequence-vector.

Is this a bug?

I'm using Emacs 20.7.3 on Windows: (i386-*-nt5.1.2600) of Thu Dec 21 2000 on
buffy.

If I try this on Emacs 21 (21.3.50.1 - i386-mingw-nt5.1.2600 of 2004-04-27
on BERATUNG4), then the Shift modifier is lost on the S-up and S-down also.
Is this intended?

How can I read the key sequence and obtain the modifier?

Thanks,

  Drew