JEP proposed to target JDK 9 (2015/1/8)

[Joseph D. Darcy]

Hello,

We may have missed some cases, but during the design of the 
javax.lang.model.* APIs we consciously tried to avoid overuse of 
covariant overrides. (Such overuse was a lesson learned from the earlier 
apt API.)

A design requirement of this API was that multiple independent 
implementation would be possible, notably javac and the Java compiler 
portion of Eclipse. The implementation model of the compiler need not 
closely resemble the interface hierarchy of javax.lang.model.*; in 
particular, we needed it to be possible to have one implementation class 
implement multiple modeling interfaces.

This requirement precludes some otherwise helpful covariant returns.

HTH,

-Joe

PS As noted in the documentation of these types, instancesof checks 
aren't always a reliable way to test what an object really is -- using 
getKind or calling a visitor are recommended.

On 1/9/2015 3:44 PM, Jonathan Gibbons wrote:
> David,
>
> That's not a goal of this JEP, but it does sound an interesting issue. 
> I would suggest filing an Enhancement Request against the API, so that 
> this can be tracked in its own right.
>
> -- Jon
>
>
> On 01/08/2015 06:05 PM, David M. Lloyd wrote:
>> Having used this API more than a bit, I think it would be super-nice 
>> if this enhancement could be extended slightly to add covariant 
>> overrides where appropriate in the javax.lang.model API, if it is at 
>> all possible to do so in a binary-compatible way.
>>
>> Specifically, where types and elements are converted to one another 
>> is a really painful part of this API; for example I'm pretty sure 
>> that DeclaredType.asElement() could return a TypeElement rather than 
>> an Element and save everyone lots of annoying casting.  Not sure if 
>> it's possible to keep the compatibility bridge method though in this 
>> particular case.  But it would be nice to at least briefly explore 
>> this path.
>>
>> On 01/08/2015 03:53 PM, mark.reinhold at oracle.com wrote:
>>> The following JEP has been placed into the "Proposed to Target"
>>> state by its owner after discussion and review:
>>>
>>>    217: Annotations Pipeline 2.0 http://openjdk.java.net/jeps/217
>>>
>>> Feedback on this proposal is more than welcome, as are reasoned
>>> objections.  If no such objections are raised by 22:00 UTC next
>>> Thursday, 15 January, or if they're raised and then satisfactorily
>>> answered, then per the JEP 2.0 process proposal [1] I'll target
>>> this JEP to JDK 9.
>>>
>>> (This information is also available on the JDK 9 Project Page [2]).
>>>
>>> - Mark
>>>
>>>
>>> [1] http://cr.openjdk.java.net/~mr/jep/jep-2.0-02.html
>>> [2] http://openjdk.java.net/projects/jdk9/
>>>
>>
>