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

[Maurizio Cimadamore]

Looks good

Maurizio

On 18/12/2018 19:52, Vicente Romero wrote:
> Hi,
>
> This bug was delayed to 13 and needed some changes. Can I have a final 
> OK before pushing it? Please see [1]
>
> Thanks,
> Vicente
>
> [1] http://cr.openjdk.java.net/~vromero/8207224/webrev.02/
>
> 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).
>>
>> Cheers
>> Maurizio
>>
>> 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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