RFR: 8343306: javac is failing to determine if a class and a sealed interface are disjoint [v6]

[Maurizio Cimadamore]

On Thu, 7 Nov 2024 17:51:15 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

>> But, according to the spec, if I have:
>> 
>> 
>> sealed class Sup { }
>> non-sealed class Sub extends Sup { }
>> 
>> 
>> Then `Sub` is not freely extensible. Becaus, even though it is neither `sealed` nor `final`, its direct superclass is `sealed`. I agree that, in spirit, `Sub` can be extended, but that's not what the JLS seems to say?
>
> I believe the spec says it is freely extensible: a class which has a sealed direct super class or super interface is freely extensible iff the is non-sealed. Maybe I am missing something?
> https://docs.oracle.com/javase/specs/jls/se22/html/jls-8.html#jls-8.1.1.2

Ah, missed this:

 A class that has a sealed direct superclass or a sealed direct superinterface is freely extensible if and only if it is declared non-sealed. 
 ```
 
 Both statements, coupled together seem a very roundabout way to do roughly what the new code is doing. I will investigate as to why this form was preferred, to make sure we're not missing anything.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21794#discussion_r1833137678