Re: A protected slot is not accessible in a subclass

[Per Bothner <per@bothner.com>]

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) ...)
-- 
	--Per Bothner
per@bothner.com   http://per.bothner.com/