gistfile1.el

(progn
  ;; edit-definitionで(setf foo)を拾えるようにする

  ;; slime-read-function-name に変更しただけ
  (defun slime-edit-definition (name &optional where)
  "Lookup the definition of the name at point.  
If there's no name at point, or a prefix argument is given, then the
function name is prompted."
  (interactive (list (slime-read-function-name "Name: ")))
  (or (run-hook-with-args-until-success 'slime-edit-definition-hooks 
                                        name where)
      (slime-edit-definition-cont (slime-find-definitions name)
                                  name where)))

  ;; setf関数名を取り出す
  (defun setf-function-name (str)
    (let ((expr (car (read-from-string str))))
    (cond ((eq 'setf (car expr))
           (format "%s" expr))
          (t (and (eq 'function (car expr))
                  (and (eq 'setf (car (cadr expr)))
                       (format "%s" (cadr expr))))))))
  
  (defun slime-function-name-at-point ()
    (let ((name (thing-at-point 'list)))
      (if (and name (setf-function-name name))
          (setf-function-name name)
          (slime-symbol-at-point))))
  
  (defun slime-read-function-name (prompt &optional query)
    (cond ((or current-prefix-arg query (not (slime-function-name-at-point)))
           (slime-read-from-minibuffer prompt (slime-function-name-at-point)))
          (t (slime-function-name-at-point)))))