RFR: JDK-8207224: Javac compiles source code despite illegal use of unchecked conversions

[Vicente Romero]

Hi,

On 12/3/18 4:13 PM, Maurizio Cimadamore wrote:
>
> Looks good - btw, if the compatibility cost proves to be too much we 
> could consider putting the new behavior behind the source switch (as 
> we did with override/hide string clash checking for some time).
>

I have modified the patch adding a guard to execute the new test only if 
source is >= 12, please take a look at the new iteration [1], I have 
also modified the CSR [2] accordingly

> Cheers
> Maurizio
>

Thanks,
Vicente

[1] http://cr.openjdk.java.net/~vromero/8207224/webrev.01/
[2] https://bugs.openjdk.java.net/browse/JDK-8214729

> On 03/12/2018 21:01, Vicente Romero wrote:
>> Hi,
>>
>> Please review the related CSR [1]
>>
>> Thanks,
>> Vicente
>>
>> [1] https://bugs.openjdk.java.net/browse/JDK-8214729
>>
>> On 12/1/18 2:46 PM, Vicente Romero wrote:
>>> Please review fix for [1] at [2]. Javac is accepting this program as 
>>> valid:
>>>
>>> class ReturnTypeSubstitutableTest {
>>>     abstract class AbstractDemo<Request extends AbstractResult, 
>>> Response extends AbstractResult> {
>>>         protected abstract Response test(Request request);
>>>     }
>>>
>>>     abstract interface AbstractResult {}
>>>
>>>     abstract interface SimpleResult extends AbstractResult {}
>>>
>>>     class Result1 implements SimpleResult {}
>>>
>>>     class OtherResult implements AbstractResult {}
>>>
>>>     public class SimpleDemo<Request extends AbstractResult, Response 
>>> extends AbstractResult> extends AbstractDemo<Request, Response> {
>>>         @Override
>>>         protected SimpleResult test(AbstractResult request) {  
>>> <----------- this method is accepted as a good override for 
>>> AbstractDemo::test
>>>             return null;
>>>         }
>>>     }
>>> }
>>>
>>> From Dan's evaluation at the bug entry [1]:
>>>
>>> Per JLS 8.4.8.3, the first method must be return-type-substitutable 
>>> for the second. This can be satisfied in 3 ways (JLS 8.4.5):
>>> - SimpleResult is a subtype of Response (no)
>>> - SimpleResult can be converted to a subtype of Response by 
>>> unchecked conversion (no)
>>> - The methods have different signatures (yep) and SimpleResult = 
>>> erasure(Response) (no)
>>>
>>> No case applies, so an error should occur. This fix syncs javac with 
>>> the spec.
>>>
>>> Thanks,
>>> Vicente
>>>
>>> [1] https://bugs.openjdk.java.net/browse/JDK-8207224
>>> [2] http://cr.openjdk.java.net/~vromero/8207224/webrev.00/
>>

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