Abstract class with fields implementing ValueObject

[Remi Forax]

----- Original Message -----
> From: "John Rose" <john.r.rose at oracle.com>
> To: "Frederic Parain" <frederic.parain at oracle.com>
> Cc: "valhalla-spec-experts" <valhalla-spec-experts at openjdk.java.net>
> Sent: Thursday, February 10, 2022 12:02:53 AM
> Subject: Re: Abstract class with fields implementing ValueObject

> That could be one of very many edge conditions in the JVMS that are not
> diagnosed directly by a validation, but that will eventually cause an error
> when the broken classfile is further used.
> 
> I don’t think there needs to be a special rule for this.  We don’t try to
> comprehensively diagnose all “impossible-to-use” classfiles.

or better we ditch ValueObject and IdentityObject ...

Rémi

> 
> On 9 Feb 2022, at 13:50, Frederic Parain wrote:
> 
>> There's a weird case that seems to be allowed by the Value Objects JVMS draft:
>>
>> An abstract class can declare non-static fields, which means it won't
>> have the ACC_PERMITS_VALUE flag set, but also declare that it implements
>> the ValueObject interface.
>>
>> The combination looks just wrong, because no class can subclass such class:
>>   - identity classes are not allowed because of the presence  of
>>     the ValueObject interface
>>   - value classes are not allowed because of the absence of
>>     ACC_PERMITS_VALUE
>>
>> I've looked for a rule that would prohibit such combination in the
>> JVMS draft but couldn't find one.
>>
>> Did I miss something?
>>
> > Fred