RFR: JDK-8240998: Implement javac changes for deconstruction patterns.

[Jan Lahoda]

Thanks Remi,

I tried to update the CSR with this warning.

Thanks,
    Jan

On 18. 03. 20 10:57, Remi Forax wrote:
> Hi Jan,
> in the CSR part,
> you don't talk about the drawbacks of using a deconstruction pattern, the syntax of a deconstruction pattern forces you to declare the number of record components you have, so adding (by example) one record component to a record will makes the code of instanceof to not compile anymore.
> 
> Let say you have
>    record Point(int x, int y);
> with the current instanceof one can write
>    if (o instanceof Point p) {
>      System.out.println(p.x() + " " + p.y());
>    }
> with a deconstruction pattern, you will write
>    if (o instanceof Point(int x, int y)) {
>      System.out.println(x + " " + y);
>    }
> 
> now if you change Point to
>    record Point(int x, int y, int z);
> the first code still compile but the second doesn't not anymore (but it still works at runtime in case of separate compilation).
> 
> It's not a big deal, it doesn't make the deconstruction pattern useless at all but I think it's something developers should be aware of.
> 
> regards,
> Rémi
> 
> ----- Mail original -----
>> De: "jan lahoda" <jan.lahoda at oracle.com>
>> À: "compiler-dev" <compiler-dev at openjdk.java.net>
>> Cc: "amber-dev" <amber-dev at openjdk.java.net>
>> Envoyé: Mercredi 18 Mars 2020 09:55:11
>> Objet: RFR: JDK-8240998: Implement javac changes for deconstruction patterns.
> 
>> Hi,
>>
>> I would like to ask for a review for a patch that implements the
>> deconstruction patterns, as described in JEP 375:
>> https://bugs.openjdk.java.net/browse/JDK-8235186
>>
>> The current specification draft is here:
>> http://cr.openjdk.java.net/~gbierman/jep375/jep375-20200316/specs/patterns-instanceof-jls.html
>>
>> For this phase, the proposal is for javac to desugar the deconstruction
>> patterns using record accessors.
>>
>> The CSR for this change is being written here:
>> https://bugs.openjdk.java.net/browse/JDK-8240999
>>
>> The proposed patch:
>> http://cr.openjdk.java.net/~jlahoda/8240998/webrev.00
>>
>> JBS: https://bugs.openjdk.java.net/browse/JDK-8240998
>>
>> Any feedback is welcome!
>>
>> Thanks,
>>       Jan