(in-package #:cl-user)

(defgeneric f (x)
  (:method (x) (declare (ignore x)) t))

(defclass c () ())

(defun test-method (&key (callers 1))
  (let ((i (make-instance 'c))
        (stop nil))
    (dotimes (i callers)
      (sb-thread:make-thread
       (lambda ()
         (loop
           (ignore-errors
            ;; Ignore errors as reported in
            ;; https://bugs.launchpad.net/sbcl/+bug/1758898
            (loop
              (f nil)
              (when stop (return))))
           (when stop (return))))
       :name (format nil "Caller")))
    (unwind-protect
        (loop
          (defmethod f ((x c)) x)
          (ignore-errors
           ;; Ignore errors as reported in
           ;; https://bugs.launchpad.net/sbcl/+bug/1758898
           (unless (and (eq (f nil) t)
                        (eq (f i) i))
             (format t "~&Transient")
             (finish-output)
             (unless (and (eq (f nil) t)
                          (eq (f i) i))
               (format t "~&Persistent")
               (finish-output)
               (return)))))
      (setf stop t))
    (assert (and (eq (f nil) t)
                 (eq (f i) i)))))

#|
Bug 2: Persistent errors where the initial dfun is computed based on the
information after the specialized method is removed and the result is stored
after the method has been added again.
|#

(test-method :callers 4)