defstruct with by-order-of-argument constructor

Hi,

using the CMU Common Lisp Snapshot 2005-11 (19C) on Linux x86, I get
undesirable results for defstructs with b-o-a constructors like the
following:

  (defstruct (foobar
               (:constructor make-foobar
                             (xxx
                              &key (aaa nil) (bbb nil)
                              &aux
                              (foobar-data xxx)
                              (aaa (or aaa
                                       (getf foobar-data :aaa)
                                       1))
                              (bbb (or bbb
                                       (getf foobar-data :bbb)
                                       (1+ aaa))))))
    (aaa (required-argument) :type fixnum)
    (bbb (required-argument) :type fixnum))

The intent is to have a b-o-a constructor with keyword arguments with
more complicated defaults; in reality, the binding for FOOBAR-DATA is
a potentially expensive computation depending on XXX.

I believe the above is valid CL (cf. CLHS 3.4.6), and Clisp in fact
accepts it and produces the desired results:

  [8]> (make-foobar nil)
  #<FOOBAR :AAA 1 :BBB 2>
  [9]> (make-foobar '(:a 5 :aaa 6))
  #<FOOBAR :AAA 6 :BBB 7>

Compiling this definition in CMUCL, however, gives me warnings and
notes about elimination of code,

  ; In: DEFSTRUCT FOOBAR
  
  ;   (GETF FOOBAR-DATA :AAA)
  ; Note: Deleting unreachable code.
  ; 
  ;   (GETF FOOBAR-DATA :BBB)
  ; Note: Deleting unreachable code.
  ; 
  ;   (1+ AAA)
  ; --> + 
  ; ==>
  ;   AAA
  ; Note: Deleting unreachable code.
  ; 
  ;   (DEFSTRUCT (FOOBAR
  ;                #)
  ;     (AAA # :TYPE FIXNUM)
  ;     (BBB # :TYPE FIXNUM))
  ; ==>
  ;   (C::%FUNCALL
  ;    #<LAMBDA #x587DC2BD  NAME= NIL  TYPE= #  WHERE-FROM= :DEFINED  VARS= #>
  ;    XXX
  ;    NIL
  ;    NIL)
  ; Warning: A possible binding of #:AAA-DEFAULTING-TEMP is not a
    (VALUES &OPTIONAL FIXNUM &REST T):
  ;   NIL
  ; 
  ; Warning: A possible binding of #:BBB-DEFAULTING-TEMP is not a
    (VALUES &OPTIONAL FIXNUM &REST T):
  ;   NIL
  ; 
  
  ; Compilation unit finished.
  ;   2 warnings
  ;   3 notes

and calls to make-foobar involving the defaulting behavior like those
given above raise TYPE-ERRORs: NIL is not of type FIXNUM.

Macroexpanding the DEFSTRUCT shows that the constructor is defined as
follows:

  (DEFUN MAKE-FOOBAR
         (XXX
          &KEY (AAA NIL) (BBB NIL)
          &AUX (FOOBAR-DATA XXX) (AAA (OR AAA (GETF FOOBAR-DATA :AAA) 1))
          (BBB (OR BBB (GETF FOOBAR-DATA :BBB) (1+ AAA))))
    (DECLARE (TYPE T XXX)
             (TYPE FIXNUM AAA)
             (TYPE FIXNUM BBB)
             (TYPE T FOOBAR-DATA)
             (TYPE FIXNUM AAA)
             (TYPE FIXNUM BBB))
    (LET ((#:G1760 (TRULY-THE FOOBAR (KERNEL:%MAKE-INSTANCE 3))))
      (SETF (KERNEL:%INSTANCE-LAYOUT #:G1760)
              (KERNEL::%GET-COMPILER-LAYOUT FOOBAR))
      (SETF (KERNEL:%INSTANCE-REF #:G1760 1) AAA)
      (SETF (KERNEL:%INSTANCE-REF #:G1760 2) BBB)
      #:G1760))

I believe the declarations to be wrong.  In my understanding the
correct expansion would be something like

  (DEFUN MAKE-FOOBAR
      (XXX
       &KEY (AAA NIL) (BBB NIL)
       &AUX (FOOBAR-DATA XXX)
       (#:AAA (OR AAA (GETF FOOBAR-DATA :AAA) 1))
       (#:BBB (OR BBB (GETF FOOBAR-DATA :BBB)
                  (LET ((AAA #:AAA)) (1+ AAA)))))
    (DECLARE (TYPE T XXX)
             (TYPE T AAA)
             (TYPE T BBB)
             (TYPE T FOOBAR-DATA)
             (TYPE FIXNUM #:AAA)
             (TYPE FIXNUM #:BBB))
    (LET ((AAA #:AAA) (BBB #:BBB))
      (LET ((#:G1760 (TRULY-THE FOOBAR (KERNEL:%MAKE-INSTANCE 3))))
        (SETF (KERNEL:%INSTANCE-LAYOUT #:G1760)
              (KERNEL::%GET-COMPILER-LAYOUT FOOBAR))
        (SETF (KERNEL:%INSTANCE-REF #:G1760 1) AAA)
        (SETF (KERNEL:%INSTANCE-REF #:G1760 2) BBB)
        #:G1760)))

, where #:AAA and #:BBB are some gensyms.  Another, more natural
option would be to simply cut the &aux arguments from the argument
list and to create the obvious let bindings, i.e.:

  (DEFUN MAKE-FOOBAR
      (XXX &KEY (AAA NIL) (BBB NIL))
    (DECLARE (TYPE T XXX)
             (TYPE T AAA)
             (TYPE T BBB))
    (LET* ((FOOBAR-DATA XXX)
           (AAA (OR AAA (GETF FOOBAR-DATA :AAA) 1))
           (BBB (OR BBB (GETF FOOBAR-DATA :BBB) (1+ AAA))))
      (DECLARE (TYPE T FOOBAR-DATA)
               (TYPE FIXNUM #:AAA)
               (TYPE FIXNUM #:BBB))
      (LET ((#:G1760 (TRULY-THE FOOBAR (KERNEL:%MAKE-INSTANCE 3))))
        (SETF (KERNEL:%INSTANCE-LAYOUT #:G1760)
              (KERNEL::%GET-COMPILER-LAYOUT FOOBAR))
        (SETF (KERNEL:%INSTANCE-REF #:G1760 1) AAA)
        (SETF (KERNEL:%INSTANCE-REF #:G1760 2) BBB)
        #:G1760)))

Comments?

Thanks in advance,

Albert.