anchor.diff:  
   
   (defmethod (setf component-entity) (entity (component Component))
  -  (with-existing-entity2 entity
  +  (with-existing-entity* entity
       (setf (slot-value component 'entity) entity)))
   
   
  
positive.code:   "Create a fresh-instance of `component-class` and add it to the components of 
     `entity`.
     `component-initargs` are supplied to `(make-instance component-class …)`."
    (with-existing-entity2 entity
      (apply #'make-instance (append (list component-class :entity entity) component-initargs))))
  
  
  
negative.code:     (f)))
  
  
  (defmacro with-existing-entity* (entity &body body)
    `(with-existing-entity ,entity (lambda (entity) ,@body)))
  
  
  