debugger error

(defclass standard-point ()
		((x :initform 0 :initarg :x)
			(y :initform 0 :initarg :y)))


(defgeneric distance-origin (point))

(defmethod distance-origin ((point1 standard-point))
		(when (and (slot-exists-p point1 'x) (slot-exists-p point1 'y))
				(sqrt (+ (expt (sb-mop:standard-instance-access point1 0) 2)
													(expt (sb-mop:standard-instance-access point1 1) 2)))))

(defgeneric distance (point1 &optional point2))

(defmethod distance (point1 &optional point2))

(defmethod distance ((point1 standard-point) &optional point2)
		(when (and (slot-exists-p point1 'x) (slot-exists-p point1 'y))
				(sqrt (+ (expt (sb-mop:standard-instance-access point1 0) 2)
													(expt (sb-mop:standard-instance-access point1 1) 2)))))

(defmethod distance ((point1 standard-point) &optional (point2 standard-point))
		(when (and (slot-exists-p point1 'x) (slot-exists-p point1 'y)
													(slot-exists-p point2 'x) (slot-exists-p point2 'y))
  (sqrt (+ (expt (- (sb-mop:standard-instance-access point2 0) (sb-mop:standard-instance-access point1 0)) 2)
											(expt (- (sb-mop:standard-instance-access point2 1) (sb-mop:standard-instance-access point1 1)) 2)))))

(defvar p1 (make-instance 'standard-point :x -3 :y 5))
(defvar p2 (make-instance 'standard-point :x 7 :y -1))

(defun test ()
		(distance p2 p1))

(test)


; in: DEFMETHOD DISTANCE (T)
;     (DEFMETHOD DISTANCE (POINT1 &OPTIONAL POINT2))
; --> LET* SB-INT:NAMED-LAMBDA
; ==>
;   #'(SB-INT:NAMED-LAMBDA (SB-PCL::FAST-METHOD DISTANCE (T))
;         (SB-PCL::.PV. SB-PCL::.NEXT-METHOD-CALL. POINT1 &OPTIONAL POINT2)
;       (DECLARE (IGNORABLE SB-PCL::.PV. SB-PCL::.NEXT-METHOD-CALL.)
;                (DISABLE-PACKAGE-LOCKS SB-PCL::PV-ENV-ENVIRONMENT))
;       (DECLARE (SB-PCL::%PARAMETER POINT1))
;       (DECLARE (TYPE T POINT1))
;       (DECLARE (IGNORABLE POINT1))
;       (SYMBOL-MACROLET ((SB-PCL::PV-ENV-ENVIRONMENT SB-PCL::DEFAULT))
;         (SB-PCL::FAST-LEXICAL-METHOD-FUNCTIONS ((POINT1)
;                                                 SB-PCL::.NEXT-METHOD-CALL.
;                                                 (POINT1) NIL
;                                                 :CALL-NEXT-METHOD-P NIL :SETQ-P
;                                                 NIL :PARAMETERS-SETQD NIL
;                                                 :METHOD-CELL (#:METHOD-CELL)
;                                                 ...)
;           (LOCALLY
;            (DECLARE #)
;            (SYMBOL-MACROLET #
;              #
;              #)))))
;
; caught STYLE-WARNING:
;   The variable POINT2 is defined but never used.
;
; compilation unit finished
;   caught 1 STYLE-WARNING condition

; file: /home/oleo/lisp/clos/packages-and-classes/standard-slot-order.lisp
; in: DEFMETHOD DISTANCE (STANDARD-POINT)
;     (DEFMETHOD DISTANCE ((POINT1 STANDARD-POINT) &OPTIONAL POINT2)
;       (WHEN (AND (SLOT-EXISTS-P POINT1 'X) (SLOT-EXISTS-P POINT1 'Y))
;         (SQRT (+ (EXPT # 2) (EXPT # 2)))))
; --> LET* SB-INT:NAMED-LAMBDA
; ==>
;   #'(SB-INT:NAMED-LAMBDA (SB-PCL::FAST-METHOD DISTANCE (STANDARD-POINT))
;         (SB-PCL::.PV. SB-PCL::.NEXT-METHOD-CALL. POINT1 &OPTIONAL POINT2)
;       (DECLARE (IGNORABLE SB-PCL::.PV. SB-PCL::.NEXT-METHOD-CALL.)
;                (DISABLE-PACKAGE-LOCKS SB-PCL::PV-ENV-ENVIRONMENT))
;       (DECLARE (SB-PCL::%PARAMETER POINT1))
;       (DECLARE (IGNORABLE POINT1))
;       (SYMBOL-MACROLET ((SB-PCL::PV-ENV-ENVIRONMENT SB-PCL::DEFAULT))
;         (SB-PCL::FAST-LEXICAL-METHOD-FUNCTIONS ((POINT1)
;                                                 SB-PCL::.NEXT-METHOD-CALL.
;                                                 (POINT1) NIL
;                                                 :CALL-NEXT-METHOD-P NIL :SETQ-P
;                                                 NIL :PARAMETERS-SETQD NIL
;                                                 :METHOD-CELL (#:METHOD-CELL)
;                                                 ...)
;           (DECLARE (SB-PCL::%CLASS POINT1 STANDARD-POINT))
;           (LOCALLY
;            (DECLARE #)
;            (SYMBOL-MACROLET #
;              #
;              #)))))
;
; caught STYLE-WARNING:
;   The variable POINT2 is defined but never used.
;
; compilation unit finished
;   caught 1 STYLE-WARNING condition

; file: /home/oleo/lisp/clos/packages-and-classes/standard-slot-order.lisp
; in: DEFMETHOD DISTANCE (STANDARD-POINT)
;     (DEFMETHOD DISTANCE
;                ((POINT1 STANDARD-POINT) &OPTIONAL (POINT2 STANDARD-POINT))
;       (WHEN
;           (AND (SLOT-EXISTS-P POINT1 'X) (SLOT-EXISTS-P POINT1 'Y)
;                (SLOT-EXISTS-P POINT2 'X) (SLOT-EXISTS-P POINT2 'Y))
;         (SQRT (+ (EXPT # 2) (EXPT # 2)))))
; --> LET* SB-INT:NAMED-LAMBDA FUNCTION
; ==>
;   (LET ((#:G1 STANDARD-POINT))
;     (LOCALLY
;      (DECLARE (MUFFLE-CONDITIONS CODE-DELETION-NOTE))
;      (SB-C::%FUNCALL #'(FAST-METHOD DISTANCE (STANDARD-POINT)) SB-PCL::.PV.
;                      SB-PCL::.NEXT-METHOD-CALL. POINT1 #:G1)))
;
; caught WARNING:
;   undefined variable: COMMON-LISP-USER::STANDARD-POINT
;
; compilation unit finished
;   Undefined variable:
;     STANDARD-POINT
;   caught 1 WARNING condition
T
*

* (distance p1)

debugger invoked on a UNBOUND-VARIABLE in thread
#<THREAD "main thread" RUNNING {1000560083}>:
  The variable STANDARD-POINT is unbound.

Type HELP for debugger help, or (SB-EXT:EXIT) to exit from SBCL.

restarts (invokable by number or by possibly-abbreviated name):
  0: [CONTINUE   ] Retry using STANDARD-POINT.
  1: [USE-VALUE  ] Use specified value.
  2: [STORE-VALUE] Set specified value and use it.
  3: [ABORT      ] Exit debugger, returning to top level.

((:METHOD DISTANCE (STANDARD-POINT)) #<STANDARD-POINT {1001AB66F3}>) [fast-method,optional]
   source: (DEFMETHOD DISTANCE
                      ((POINT1 STANDARD-POINT)
                       &OPTIONAL (POINT2 STANDARD-POINT))
             (WHEN
                 (AND (SLOT-EXISTS-P POINT1 'X) (SLOT-EXISTS-P POINT1 'Y)
                      (SLOT-EXISTS-P POINT2 'X) (SLOT-EXISTS-P POINT2 'Y))
               (SQRT (+ (EXPT (- # #) 2) (EXPT (- # #) 2)))))
0]