hg: amber/amber: adding method Class::isRecord

[Brian Goetz]

It’s not like the only two options for recording record-ness in the classfile are ACC_RECORD and a nominal superclass; we can use attributes too.  

Similarly, there’s nothing that stops us from making an exception of AbstractRecord as a super type of value types, as it has no state (which it doesn’t.)  Or make AbstractRecord an interface.  Or a whole host of options in between, such as a Value interface with a sub-interface of ValueRecord.  

So I’ll discard all the “can’ts” and “problems” and restate this as:

 - We should bear in mind that we want records of both value- and object-nature, and ensure that there is a strategy to translate them and reflect over them.  

Which I would agree with.


> On Jul 12, 2018, at 4:29 PM, forax at univ-mlv.fr wrote:
> 
> Thinking a little bit more about record and the abstract class AbstractRecord,
> the problem with the presence of AbstractRecord is that it means can not have 'value record', a record which are value class because a value class can not inherits from an abstract class.
> 
> Rémi
> 
> De: "Vicente Romero" <vicente.romero at oracle.com>
> À: "Brian Goetz" <brian.goetz at oracle.com>, "Remi Forax" <forax at univ-mlv.fr>
> Cc: "amber-dev" <amber-dev at openjdk.java.net>
> Envoyé: Mercredi 11 Juillet 2018 23:58:26
> Objet: Re: hg: amber/amber: adding method Class::isRecord
> 
> 
> On 07/11/2018 05:08 PM, Brian Goetz wrote:
> I don’t think burning an ACC_RECORD flag is a terribly good use of some very expensive real estate.
> 
> But, I had a different wonder: why not just do this from the Java side as:
> 
>     boolean isRecord() { return AbstractRecord.class.isAssignableFrom(this); } 
> 
> yep that was what Paul also suggested in an offline conversation. I have reversed the original patch and applied redone this as:
> 
> public boolean isRecord() {
>     return this.getSuperclass() == java.lang.AbstractRecord.class;
> }
> Vicente
> 
> ?
> 
> 
> 
> On Jul 11, 2018, at 4:54 PM, Remi Forax <forax at univ-mlv.fr> <mailto:forax at univ-mlv.fr> wrote:
> 
> Hi Vicente,
> usually for the Java side (Class.java), to avoid a native call, one of the bit of the class modifier flags, let's call it ACC_RECORD is reserved.
> 
> Rémi
> 
> ----- Mail original -----
> De: "Vicente Romero" <vicente.romero at oracle.com> <mailto:vicente.romero at oracle.com>
> À: "amber-dev" <amber-dev at openjdk.java.net> <mailto:amber-dev at openjdk.java.net>
> Envoyé: Mercredi 11 Juillet 2018 22:28:10
> Objet: hg: amber/amber: adding method Class::isRecord
> Changeset: 2c5938e024ed
> Author:    vromero
> Date:      2018-07-11 13:02 -0700
> URL:       http://hg.openjdk.java.net/amber/amber/rev/2c5938e024ed <http://hg.openjdk.java.net/amber/amber/rev/2c5938e024ed>
> 
> adding method Class::isRecord
> 
> ! make/hotspot/symbols/symbols-unix
> ! src/hotspot/share/classfile/systemDictionary.hpp
> ! src/hotspot/share/classfile/vmSymbols.hpp
> ! src/hotspot/share/include/jvm.h
> ! src/hotspot/share/oops/klass.cpp
> ! src/hotspot/share/oops/klass.hpp
> ! src/hotspot/share/prims/jvm.cpp
> ! src/java.base/share/classes/java/lang/Class.java
> ! src/java.base/share/native/libjava/Class.c
> 
>