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bug#56751: Protocol of parent record type is ignored
From: |
Maxime Devos |
Subject: |
bug#56751: Protocol of parent record type is ignored |
Date: |
Sun, 24 Jul 2022 22:56:58 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 |
(import (rnrs records syntactic)
(rnrs base))
(define-record-type
(#{I have one field, but no need to set it, I'll do it myself}#
make-1 type-1?)
(fields (immutable #{field with a fixed value}# #{get first field
value}#))
(protocol
(lambda (%make)
(lambda ()
(#;(%make) ;; XXX unlike what is documented, this needs to be:
%make
;; instead. Bug in inmplementation or documentation? Not the issue
;; I wanted to note though.
"some value")))))
(assert (string=? (#{get first field value}# (make-1)) "some value")) ; ok
(define-record-type (#{the subtype}# make-2 type-2?)
(parent #{I have one field, but no need to set it, I'll do it myself}#))
;; The problem:
;;
;; Guile seems to have forgotten that the protocol of the supertype,
;; and hence asks for a value for the argument even though the protocol
;; of the original record type normally would give it a value.
;; (Ok, this is interpretation for the symptoms, I haven't yet tested
this against
;; the source code).
;;
;; This manifests as make-2 havng arity 1 though it should have arity 1:
#;
(assert (equal? (#{get first field value}# (make-2) "some value"))) ;;
--> wrong number of arguments to #<procedure ...>
;; We can due to the bug also break the abstraction: (see assert failure)
(assert (equal? (#{get first field value}# (make-2
'break-the-abstraction)) "some value")) ;; --> wrong number of arguments
to #<procedure ...>
;; Note: if I explicitly write the protocol for the subtype, then all
the problems disappear
;; (work-around). For an example in the wild, see the supertype
<lost-and-found> at
;;
<https://git.gnunet.org/gnunet-scheme.git/tree/gnu/gnunet/concurrency/lost-and-found.scm>
;; and the subtype at
<https://git.gnunet.org/gnunet-scheme.git/tree/gnu/gnunet/dht/client.scm#n583>
;; (Not the best example, as I give the new fields default values as
well, but you get the idea.)
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