defmethod congruency checks

[rme]

(From Pascal Costanza, ​http://clozure.com/pipermail/openmcl-devel/2009-September/010353.html)

Clozure Common Lisp seems to be too eager in its checking of congruency of generic function lambda lists and those of their methods.

Consider the following example:

? (defgeneric foo (a b c))
#<STANDARD-GENERIC-FUNCTION FOO #x30004125B93F>
? (add-method
   #'foo
   (make-instance 'standard-method
     :qualifiers '()
     :specializers (list (find-class 't) (find-class 't) (find-class 't))
     :lambda-list '(a b c)
     :function (lambda (&rest args) (print args))))
> Error: Lambda list of method #<STANDARD-METHOD NIL (T T T)>
>        is incompatible with that of the generic function FOO.
>        Method's lambda-list : (A B C)
>        Generic-function's   : (A B C)

While executing: CCL::CHECK-DEFMETHOD-CONGRUENCY, in process  
listener(1).

Indeed, check-defmethod-congruency uses the method-function to check for congruency, while it should actually use method-lambda-list for that purpose (at least in non-standard cases).

As far as I can tell at the moment, this is the only remaining step so that I can provide compatibility in Closer to MOP of the generic function invocation protocol to the specification in AMOP.

[lovesan]

It seems that CCL compares method-function's lambda-list with that of generic-function because method-function's one is actually congruent with that of the method.

I'm not sure what does AMOP specify on this case, but in SBCL and clisp, for example, standard-method's method-function takes two arguments - a list of method arguments, and a list of next methods(so, it is possible for method's function to control dispatch mechanism to some extent).

I'm currently working on an open-source library, which allows Common Lisp to interoperate with Microsoft's COM. ​https://github.com/Lovesan/doors

This library heavily utilizes MOP, so i've been forced to implement quite hacky workaround for CCL support.

Hope, CCL will improve its MOP implementation soon.

[gb]

(In [14626]) Use the METHOD object's lambda-list (not the METHOD-FUNCTION's) when determining lambda-list congruency.

This seems to fix ticket:600.