Re: define-compiler-macro and funcall forms.

On 3/14/15 9:26 PM, Mark Cox wrote:
> G'day,
>
> The compiler macro functions created by CMUCL using
> define-compiler-macro do not correctly handle funcall forms in cases
> where the compiler macro function returns the input form. This is
> demonstrated with the following example:

Thanks for the bug report!  Sorry it took so long to respond.  Occupied
with various unrelated things, but I should have a bit more free time soon.

In the mean time, it would be great if you could file a bug on this (and
the function coercing issue) on cmucl's issues tracker: 
https://gitlab.common-lisp.net/cmucl/cmucl/issues.  (Don't worry about
it if you can't. I will file the issue eventually, if I don't forget.)

Thanks again for the reports!

>
>   (defun square (x)
>     (expt x 2))
>
>   (define-compiler-macro square (&whole form arg)
>     (declare (ignore arg))
>     form)
>
>   (funcall (compiler-macro-function 'square) '(square x) nil)
>   => (SQUARE X)
>
>   (funcall (compiler-macro-function 'square) '(funcall #'square x) nil)
>   => (#'SQUARE X)
>
> The cause of this error is due to a bug in the body argument returned
> by lisp::parse-defmacro.
>
>   (nth-value 0 (lisp::parse-defmacro '(&whole form arg) 'my-form '(form)
>                                      'square 'define-compiler-macro))
>   => (let* ((my-form (if (progn
>                            (not (and (listp my-form)
>                                      (eq 'funcall (car my-form)))))
>                          my-form
>                          (progn
>                            (setf my-form (cdr my-form))))))
>        (unless (lisp::list-length-bounded-p (the list (cdr my-form)) 1 1)
>          (lisp::do-arg-count-error 'define-compiler-macro
>            'square
>            (cdr my-form)
>            '(&whole form arg)
>            1
>            1))      
>        (let* ((form my-form) (arg (car (cdr my-form))))
>          form))
>
> The body above is evaluated in a lexical environment where MY-FORM is
> bound to '(funcall #'square x). A new binding of MY-FORM is introduced
> by the first LET* in the body above such that MY-FORM is (cdr '(#'square x)).
> This value is then bound to the &WHOLE symbol FORM specified in the input
> lambda list to PARSE-DEFMACRO.
>
> Thanks
> Mark
>
> [1]. http://www.lispworks.com/documentation/HyperSpec/Body/m_define.htm
>
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