anchor.diff:  generated class containing the specialized hostlists and the original
   `blocker-mode'."
   
  -  (unless (find-class name nil)
  -    (error "define-configuration argument ~a is not a known class." name))
  -  (let ((temp-name (gentemp (string name))))
  +  (let* ((final-name (intern (str:concat "REPLACEME-" (string name)) (symbol-package name)))
  +         (temp-name (gentemp (string final-name) (symbol-package name))))
  +    (dolist (name (list name final-name))
  +      (unless (find-class name nil)
  +        (error "define-configuration argument ~a is not a known class." name)))
       `(progn
          (define-class ,temp-name ()
  -         ,(loop with super-class = (closer-mop:ensure-finalized (find-class name))
  +         ,(loop with super-class = (closer-mop:ensure-finalized (find-class final-name))
                   for slot in (first slots)
                   for known-slot? = (find (first slot) (mopu:slot-names super-class))
                   for initform = (and known-slot?
  
positive.code:                                                       ,(cadr slot))
                                                      ,initform))
                  else do
                    (log:warn "Undefined slot ~a in ~a" (first slot) name))
           (:accessor-name-transformer #'class*:name-identity))
         (defclass ,name ,(cons temp-name
                           (mapcar #'class-name
                                   (mopu:direct-superclasses name))) ()))))
  
  (export-always 'load-system)
  (defun load-system (system)
  
negative.code:   "Helper macro to customize NAME class slots.
  
  Classes can be modes or a core class like `browser', `buffer', `minibuffer',
  `window'.  Note that the classes must _not_ be prefixed by 'REPLACEME-'.
  
  The `%slot-default' variable is replaced by the slot initform.
  
  Example that sets some defaults for all buffers:
  
  \(define-configuration buffer
    ((status-buffer-height 24)
     (default-modes (append '(vi-normal-mode) %slot-default))))
  
  