[racket] Unexpected results with impersonators and make-keyword-procedure

Oops... I'll push a repair soon.

Thanks!

At Mon, 9 Mar 2015 16:58:41 -0400, Scott Moore wrote:
> Hi Matthew,
> 
> Thanks for working on this so quickly! Unfortunately, It looks like there is a 
> bug in the fix that causes segfaults when checking impersonator properties on 
> keyword procedures that are not impersonators. I’ve included a small test case 
> below.
> 
> Thanks again,
> Scott
> 
> #lang racket
> 
> (define-values (prop:my-prop my-prop? my-prop-accessor)
>   (make-impersonator-property 'my-prop))
> 
> (define kwp
>   (make-keyword-procedure 
>                  (λ (kwds kwd-args . other-args)
>                    (printf "Keywords: ~a~n" kwds)
>                    (printf "Keyword arguments: ~a~n" kwd-args)
>                    (printf "Other arguments: ~a~n" other-args))
>                  (λ args
>                    (printf "Arguments: ~a~n" args))))
> 
> (my-prop? kwp)
> 
> > On Mar 8, 2015, at 10:12 PM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> > 
> > I agree that this is a bug --- specific to impersonators that are not
> > chaperones --- and I've pushed a repair to the Git repo.
> > 
> > The general repair was to make impersonator-property predicates and
> > accessors sensitive to `prop:impersonator-of`. When a structure
> > impersoator does not have a particular impersonator property, but its
> > structure has the `prop:impersonator-of` property, then the structure
> > produced by `prop:impersonator-of` is checked (recursively). That
> > change fixes the problem with keyword procedures, because
> > `impersonator-procedure` on keyword-acepting procedure is implemented
> > through an internal structure type that has `prop:impersonator-of`.
> > 
> > Thanks for the report!
> > 
> > At Fri, 6 Mar 2015 20:04:10 -0500, Scott Moore wrote:
> >> Hi,
> >> 
> >> I've run into some strange behavior with the interaction between
> >> impersonators and make-keyword-procedure. I expect that when not invoked
> >> with keywords, the result of make-keyword-procedure and a lambda with the
> >> same form should be equivalent. Instead, they behave differently when
> >> impersonated. I have included a small module that demonstrates the issue
> >> below. I expect that the two checks at the bottom should succeed.
> >> 
> >> Thanks,
> >> Scott
> >> 
> >> #lang racket
> >> 
> >> (require rackunit)
> >> 
> >> (define-values (prop:my-prop my-prop? my-prop-accessor)
> >>  (make-impersonator-property 'my-prop))
> >> 
> >> (define (mark-with-my-prop val)
> >>  (impersonate-procedure
> >>   val
> >>   #f
> >>   prop:my-prop
> >>   #t))
> >> 
> >> (define (mark-fun-mkp f)
> >>  (mark-with-my-prop
> >>   (make-keyword-procedure
> >>    (λ (kwds kwd-args . other-args)
> >>      (keyword-apply f kwds kwd-args other-args))
> >>    (λ args
> >>      (apply f args)))))
> >> 
> >> (define (mark-fun-lambda f)
> >>  (mark-with-my-prop
> >>   (λ args
> >>     (apply f args))))
> >> 
> >> (define (dummy-impersonator val)
> >>  (make-keyword-procedure
> >>   (λ (kwds kwd-args . other-args)
> >>     (apply values kwd-args other-args))
> >>   (λ args
> >>     (apply values args))))
> >> 
> >> (define marked-mkp (mark-fun-mkp display))
> >> (define marked-lambda (mark-fun-lambda display))
> >> 
> >> (check-eq? (my-prop? marked-lambda) (my-prop? marked-mkp))
> >> (check-eq? (my-prop? (impersonate-procedure marked-lambda
> >> (dummy-impersonator marked-lambda)))
> >>           (my-prop? (impersonate-procedure marked-mkp (dummy-impersonator
> >> marked-mkp))))
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