GNU bug report logs - #46175
Redefinable classes clobber custom slot options

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: "Thompson, David" <dthompson2 <at> worcester.edu>
Subject: bug#46175: closed (Re: bug#46175: Redefinable classes clobber
 custom slot options)
Date: Sat, 20 Mar 2021 19:03:02 +0000

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Your bug report

#46175: Redefinable classes clobber custom slot options

which was filed against the guile package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 46175 <at> debbugs.gnu.org.

-- 
46175: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=46175
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Andy Wingo <wingo <at> pobox.com>
To: "Thompson, David" <dthompson2 <at> worcester.edu>
Cc: 46175-done <at> debbugs.gnu.org
Subject: Re: bug#46175: Redefinable classes clobber custom slot options
Date: Sat, 20 Mar 2021 20:02:29 +0100

On Fri 29 Jan 2021 17:43, "Thompson, David" <dthompson2 <at> worcester.edu> writes:

> The compute-slots method for <redefinable-class> does a transformation
> of #:allocation #:instance slots to #:allocation #:virtual slots, but
> in doing so it discards all slot options besides the standard ones.
> This means that a metaclass that inherits from <redefinable-class>
> won't work as expected if it relies upon custom slot options.

Thanks for the report; patch applied!

Andy

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From: "Thompson, David" <dthompson2 <at> worcester.edu>
To: bug-guile <at> gnu.org
Subject: Redefinable classes clobber custom slot options
Date: Fri, 29 Jan 2021 11:43:35 -0500

[Message part 4 (text/plain, inline)]

The compute-slots method for <redefinable-class> does a transformation
of #:allocation #:instance slots to #:allocation #:virtual slots, but
in doing so it discards all slot options besides the standard ones.
This means that a metaclass that inherits from <redefinable-class>
won't work as expected if it relies upon custom slot options.

Test case:

    (use-modules (oop goops)
                 (srfi srfi-111))

    (define-class <meta> (<class>))

    (define (boxed-slot? slot)
      (get-keyword #:box? (slot-definition-options slot)))

    (define-method (compute-getter-method (class <meta>) slot)
      (if (boxed-slot? slot)
          (make <method>
            #:specializers (list class)
            #:procedure (let ((slot-name (slot-definition-name slot)))
                          (lambda (obj)
                            (unbox (slot-ref obj slot-name)))))
          (next-method)))

    (define-method (compute-setter-method (class <meta>) slot)
      (if (boxed-slot? slot)
          (make <method>
            #:specializers (list class <top>)
            #:procedure (let ((slot-name (slot-definition-name slot)))
                          (lambda (obj value)
                            (set-box! (slot-ref obj slot-name) value))))
          (next-method)))

    (define-class <redefinable-meta> (<meta> <redefinable-class>))

    (define-class <foo> ()
      (bar #:accessor bar #:box? #t #:init-form (box 123))
      #:metaclass <meta>)

    (define-class <redefinable-foo> ()
      (bar #:accessor bar #:box? #t #:init-form (box 123))
      #:metaclass <redefinable-meta>)

    ;; This works:
    (pk (+ (bar (make <foo>)) 456))

    ;; This throws an error:
    (pk (+ (bar (make <redefinable-foo>)) 456))

Attached is a patch that preserves all slot options that redefinable
classes do not need to alter, including custom ones.  How does it
look?

- Dave

[0001-goops-Preserve-all-slot-options-in-redefinable-class.patch (text/x-patch, attachment)]

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