Updated Draft specs for JEP 359 (Records)

[Gavin Bierman]

A further updated draft language spec for JEP 359 (Records) is available at:

http://cr.openjdk.java.net/~gbierman/jep359/jep359-20191125/specs/records-jls.html

along with an updated JVMS spec:

http://cr.openjdk.java.net/~gbierman/jep359/jep359-20191125/specs/records-jvms.html

(Thanks to Maurizio, Alex, Tagir and others for feedback.)

Main change is around the definition of canonical constructor and accessor methods. The text has changed quite a bit, but this is mainly at the surface. Hopefully this new definition is easier to understand than before and removes some corner cases (most of which were of the “which error should arise from this program?”).

The idea for canonical constructors is as follows (it’s very similar for accessor methods): You are a constructor. If your signature is override-equivalent to the constructor signature derived from the record declaration in the obvious way, then you are considered a canonical constructor. (This also means that there can’t be more than one canonical constructor.) In addition, as you have been identified as a canonical constructor, you must satisfy some additional requirements, otherwise there is a compile-time error. These are:
The types of the formal parameters in the formal parameter list of the canonical constructor must be identical to the declared type of the corresponding record component.
A canonical constructor must not be generic (8.8.4).
A canonical constructor must be declared public.
A canonical constructor must not have a throws clause.
The body of a canonical constructor must not contain an explicit constructor invocation statement (8.8.7.1).
All the other rules for a constructor in a normal class declaration must be satisfied (8.8).
We could relax some of these rules - I know Remi would like to change the third one :-) The first one is another candidate. I propose that we try these ones out in the preview, and during the preview period you can send us your experience kicking the tires with these. [One reason for this refactoring is that should we decide to relax some of these restrictions, it is a relatively simple change to the spec, which will make our lives easier for subsequent JDKs.]

Many thanks,
Gavin



> On 21 Nov 2019, at 15:01, Gavin Bierman <gavin.bierman at oracle.com> wrote:
> 
> A hopefully final draft language spec for JEP 359 (Records) is available at:
> 
> http://cr.openjdk.java.net/~gbierman/jep359/jep359-20191121/specs/records-jls.html <http://cr.openjdk.java.net/~gbierman/jep359/jep359-20191121/specs/records-jls.html>  
> 
> This incorporates (I hope!) all the very helpful suggestions from everyone on these lists - many thanks. 
> 
> As always - any further comments/thoughts/bugs most welcome!
> 
> Gavin
> 
>> On 31 Oct 2019, at 14:17, Gavin Bierman <gavin.bierman at oracle.com <mailto:gavin.bierman at oracle.com>> wrote:
>> 
>> An updated draft language spec for JEP 359 (Records) is available at:
>> 
>> http://cr.openjdk.java.net/~gbierman/jep359/jep359-20191031/specs/records-jls.html <http://cr.openjdk.java.net/~gbierman/jep359/jep359-20191031/specs/records-jls.html>
>> 
>> (Alongside is a draft JVM spec for this feature:
>> 
>> http://cr.openjdk.java.net/~gbierman/jep359/jep359-20191031/specs/records-jvms.html <http://cr.openjdk.java.net/~gbierman/jep359/jep359-20191031/specs/records-jvms.html>
>> 
>> )
>> 
>> As always, please email me any comments/thoughts/bugs.
>> 
>> Thanks,
>> Gavin
>> 
>> 
>>> On 23 Aug 2019, at 22:25, Gavin Bierman <gavin.bierman at oracle.com <mailto:gavin.bierman at oracle.com>> wrote:
>>> 
>>> A draft language spec for records is available at:
>>> 
>>> http://cr.openjdk.java.net/~gbierman/8222777/8222777-20190823/specs/records-jls.html <http://cr.openjdk.java.net/~gbierman/8222777/8222777-20190823/specs/records-jls.html>
>>> 
>>> This spec doesn’t yet discuss varargs records - to appear in the next draft.
>>> 
>>> All comments welcomed!
>>> 
>>> Thanks,
>>> Gavin
>> 
> 

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