Re: A protected slot is not accessible in a subclass

[Panicz Maciej Godek <godek.maciek@gmail.com>]

Thanks for the reply!

I tried this:


(define-simple-class S (gnu.mapping.Symbol)
   ((*init*)
    (invoke-special gnu.mapping.Symbol (this) '*init*
(("foo":toString):intern) gnu.mapping.Namespace:EmptyNamespace)
 (set! (field (this) 'name) (("bar":toString):intern))))


(define s::S(S))

but it gives a similar error:

java.lang.RuntimeException: no such field name in S
        at gnu.kawa.reflect.SlotSet.apply(SlotSet.java:115)
        at gnu.kawa.reflect.SlotSet.apply3(SlotSet.java:120)
        at S.<init>(tty:14)

I also tried replacing

(field (this) 'name)

with



(field (as gnu.mapping.Symbol (this) 'name)

but it didn't change anything.

Outside the setter context, (field (this) 'name) works fine.

BTW my previous message contained an error - instead of

(invoke-special gnu.mapping.Symbol (("foo":toString):intern)
gnu.mapping.Namespace:EmptyNamespace)

I should of course have written

(invoke-special gnu.mapping.Symbol (this) '*init* (("foo":toString):intern)
gnu.mapping.Namespace:EmptyNamespace)

I mistakenly omitted it while I was writing the message.

pt., 25 mar 2022, 05:56 użytkownik Per Bothner <per@bothner.com> napisał:

>
> On 3/24/22 15:14, Panicz Maciej Godek via Kawa wrote:
> > I get the following error:
> >
> > slot 'name' in gnu.mapping.Symbol not accessible here
> >
> > What are the rules for accessing protected members in Kawa?
>
> The rules are supposed to be the same as in Java
> (because those rules are enforced by the JVM).
> However, those rules are actually a bit complicated:
> https://docs.oracle.com/javase/specs/jls/se11/html/jls-6.html#jls-6.6.2
>
> In this case there is a bug in Kawa. It treats
>    (set! name ...)
> as equivalent to:
>    (set! (this):name ...)
> which is fine.
>
> However, there seems to a problem where Kawa thinks (this) has the type
> Symbol (because that is
> where name is defined) rather than class S.  And this violates the rule:
>
>      If the access is by (i) a qualified name of the form
> ExpressionName.Id or TypeName.Id, or
>      (ii) a field access expression of the form Primary.Id, then access to
> the instance field Id
>      is permitted if and only if the qualifying type is S or a subclass of
> S.
>
>      The qualifying type is the type of the ExpressionName or Primary, or
> the type denoted by TypeName.
>
> A work-around is to use the field special procedure:
>
>     (set! (field (this) 'name) ...)


>