Track undefined function warnings in SBCL

undef-warning.lisp

; put this in my .sbclrc file.
; useful idea I had, rebind defun to keep track
; of functions that have been referenced but not yet
; defined. Loosely inspired by Utopian.
(setf (macro-function 'cl-defun) (macro-function 'defun))
(defparameter *undefined-functions* nil)
(handler-bind
  ((warning
     (lambda (w)
       (declare (ignorable w))
       (invoke-restart 'muffle-warning)))
   (sb-ext:symbol-package-locked-error
     (lambda (e)
       (declare (ignorable e))
       (invoke-restart 'continue))))
  (defmacro defun (name args &body body)
    `(handler-bind
       ((sb-int:simple-style-warning
          (lambda (w)
            (let ((c (simple-condition-format-control w))
                  (a (simple-condition-format-arguments w)))
              (when (and (equal c "undefined ~(~A~): ~S")
                         (eql (length a) 2)
                         (eql (first a) :function))
                (setf *undefined-functions*
                      (union *undefined-functions* (cdr a))))))))
       (eval '(cl-defun ,name ,args ,@body))
       (setf *undefined-functions*
             (set-difference *undefined-functions* '(,name)))
       (if (plusp (length *undefined-functions*))
           (format t
                   "; REMINDER: you still have undefined functions ~S"
                   *undefined-functions*)))))
(defun typo (fn)
  "Remove undef fn reminder manually, e.g. due to typos."
  (setf *undefined-functions*
        (set-difference *undefined-functions* (list fn))))