The function SB-C::%STRUCTURE-IS-A is undefined.

[Paul F. Dietz]

(in-package :cl-user)

(defstruct bug024 x)

(let ((s (make-bug024 :x 17)))
  (eval
   `(defun foo (a)
      (declare (OPTIMIZE (SPEED 3) (SAFETY 1) (DEBUG 1) (SPACE 1)))
      (declare (type (member #:a #\x ,s) a))
      (bug024-x a)))
  (format t "~a~%" (foo s)))

==>

The function SB-C::%STRUCTURE-IS-A is undefined.
   [Condition of type UNDEFINED-FUNCTION]
[...]
Backtrace:
  0: ("undefined function" #<SB-KERNEL:LAYOUT (ID=1225) for COMMON-LISP-USER::BUG024 {50417483}> #<SB-KERNEL:LAYOUT (ID=1225) for COMMON-LISP-USER::BUG024 {50417483}>)
  1: (COMMON-LISP-USER::FOO #S(COMMON-LISP-USER::BUG024 :X 17))

[Paul F. Dietz (paul-f-dietz)]

Also:

(let ((s (make-bug024 :x 14)))
           (compile nil
                    `(lambda (a)
                       (when (typep a '(member #\8 ,s))
                         (bug024-x a)))))

==>

; in: LAMBDA (A)
; (BUG024-X A)
;
; caught STYLE-WARNING:
; Lisp error during constant folding:
; The function SB-C::%STRUCTURE-IS-A is undefined.
;
; compilation unit finished
; caught 1 STYLE-WARNING condition
#<FUNCTION (LAMBDA (A)) {52DBD37B}>
T
NIL