[no subject]

[RZ at MIT-MC (Richard E. Zippel)]

(desetq (a b c) a)
fails.  b gets bound to (cdar a) ....  There is an
optimization that tries to save something between
(desetq (a b c) (f a)) and (desetq (a b c) a)..

In the first case a gensym gets bounnd to (f a)..  If this happended
in the second case thigns would win.

Also SETF seems to lose in the compiler.  Try compiling
(defmacro state (node) `(car ,node))
(defun foo (x y)
   (setf (state x) y)
   (bar x))