Record Component attributes

[Remi Forax]

----- Mail original -----
> De: "Remi Forax" <forax at univ-mlv.fr>
> À: "Brian Goetz" <brian.goetz at oracle.com>
> Cc: "amber-spec-experts" <amber-spec-experts at openjdk.java.net>
> Envoyé: Mercredi 9 Octobre 2019 18:44:23
> Objet: Re: Record Component attributes

> ----- Mail original -----
>> De: "Brian Goetz" <brian.goetz at oracle.com>
>> À: "Remi Forax" <forax at univ-mlv.fr>, "amber-spec-experts"
>> <amber-spec-experts at openjdk.java.net>
>> Envoyé: Mercredi 9 Octobre 2019 17:59:56
>> Objet: Re: Record Component attributes
> 
>>> just to be sure, do we agree that a record component can be deprecated,
>>> synthetic, have a generic signature, have unknown attributes, have annotation
>>> and type annotations ?
>> 
>> Deprecated: not clear what this would mean, since removing a component
>> is not a BC or SC change, and therefore removal seems unlikely, but I
>> suppose deprecation could be a "stay away" warning sign for that
>> component?  On the fence.
>> 
>> Synthetic: I think this is a no.  The philosophy is: a record is a class
>> whose representation and API are both derived from the state
>> description.  Having a synthetic component would be weird (same reason
>> we don't have inner records.)
>> 
>> Generic signature: yes, definitely.
>> 
>> Unknown attributes: I believe that Dan had an opinion here, as reflected
>> in the current spec draft?
>> 
>> Declaration and type annotations: yes, definitely.
> 
> given it's the class format representation, i will wear my JVM runtime
> implementer hat :
> 
> There a lot of languages that have default value for parameters, so for
> constructor parameters,
> for those it makes sense to be able to deprecate a record component if at the
> same time you provide a default value for this component.
> 
> for synthetic, a synthetic component is a component that the VM (or the
> reflection) sees but that javac doesn't see. Reified generics stored as
> parameter like in Swift is a case where you may not want javac to see your ugly
> refiied type/witness type/etc.

and answering to myself,
javac doesn't directly access to the record component, it accesses to the generated fields/methods so making the record component synthetic or not has no impact on javac, so marking a record component Synthetic seems useless.

Rémi

> 
>> 
>>>
>>> so the attributes with a special meaning are
>>>    SIGNATURE, DEPRECATED, SYNTHETIC, RUNTIME_VISIBLE_ANNOTATIONS,
>>>    RUNTIME_VISIBLE_TYPE_ANNOTATIONS, RUNTIME_INVISIBLE_ANNOTATIONS and
>>>    RUNTIME_INVISIBLE_TYPE_ANNOTATIONS.
>>>
>>> said differently, it's all the attributes allowed on a field but CONSTANTVALUE
>>> which makes no sense on a record component.
>>>
>>> regards,
> > > Rémi