(defmacro with-unlocked-box ((value box) &body body)
  "An attempt at some sort of thread safety trick. The idea is that we
can only write to the locked value inside this macro body. It might work.
Maybe.

(defvar *box* (make-locked-box :value 42))

(with-thread (:name \"Evil fighting thread!\")
  (loop
   (setf v :woohoo-type-error-time)
   (sleep 0.01)))

(with-unlocked-box (v *box*)
  (setf v 12300)
  (+ v 45)) ; => 12345 (always)
"
  (alexandria:once-only (box)
    `(bt:with-lock-held ((locked-box-lock ,box))
       (symbol-macrolet ((,value (locked-box-value ,box)))
         . ,body))))