- ;; KLUDGE: this double expansion is quite a monumental
- ;; workaround: it comes about because of a fantastic interaction
- ;; between the processing rules of CLHS 3.2.3.1 and the
- ;; bizarreness of MAKE-METHOD-LAMBDA.
- ;;
- ;; MAKE-METHOD-LAMBDA can be called by the user, and if the
- ;; lambda itself doesn't refer to outside bindings the return
- ;; value must be compileable in the null lexical environment.
- ;; However, the function must also refer somehow to the
- ;; associated method object, so that it can call NO-NEXT-METHOD
- ;; with the appropriate arguments if there is no next method --
- ;; but when the function is generated, the method object doesn't
- ;; exist yet.
- ;;
- ;; In order to resolve this issue, we insert a literal cons cell
- ;; into the body of the method lambda, return the same cons cell
- ;; as part of the second (initargs) return value of
- ;; MAKE-METHOD-LAMBDA, and a method on INITIALIZE-INSTANCE fills
- ;; in the cell when the method is created. However, this
- ;; strategy depends on having a fresh cons cell for every method
- ;; lambda, which (without the workaround below) is skewered by
- ;; the processing in CLHS 3.2.3.1, which permits implementations
- ;; to macroexpand the bodies of EVAL-WHEN forms with both
- ;; :COMPILE-TOPLEVEL and :LOAD-TOPLEVEL only once. The
- ;; expansion below forces the double expansion in those cases,
- ;; while expanding only once in the common case.
- (eval-when (:load-toplevel)
- (%defmethod-expander ,name ,qualifiers ,lambda-list ,body))
- (eval-when (:execute)
- (%defmethod-expander ,name ,qualifiers ,lambda-list ,body)))))
+ ;; KLUDGE: this double expansion is quite a monumental
+ ;; workaround: it comes about because of a fantastic interaction
+ ;; between the processing rules of CLHS 3.2.3.1 and the
+ ;; bizarreness of MAKE-METHOD-LAMBDA.
+ ;;
+ ;; MAKE-METHOD-LAMBDA can be called by the user, and if the
+ ;; lambda itself doesn't refer to outside bindings the return
+ ;; value must be compileable in the null lexical environment.
+ ;; However, the function must also refer somehow to the
+ ;; associated method object, so that it can call NO-NEXT-METHOD
+ ;; with the appropriate arguments if there is no next method --
+ ;; but when the function is generated, the method object doesn't
+ ;; exist yet.
+ ;;
+ ;; In order to resolve this issue, we insert a literal cons cell
+ ;; into the body of the method lambda, return the same cons cell
+ ;; as part of the second (initargs) return value of
+ ;; MAKE-METHOD-LAMBDA, and a method on INITIALIZE-INSTANCE fills
+ ;; in the cell when the method is created. However, this
+ ;; strategy depends on having a fresh cons cell for every method
+ ;; lambda, which (without the workaround below) is skewered by
+ ;; the processing in CLHS 3.2.3.1, which permits implementations
+ ;; to macroexpand the bodies of EVAL-WHEN forms with both
+ ;; :COMPILE-TOPLEVEL and :LOAD-TOPLEVEL only once. The
+ ;; expansion below forces the double expansion in those cases,
+ ;; while expanding only once in the common case.
+ (eval-when (:load-toplevel)
+ (%defmethod-expander ,name ,qualifiers ,lambda-list ,body))
+ (eval-when (:execute)
+ (%defmethod-expander ,name ,qualifiers ,lambda-list ,body)))))