Nested generics don't compile in 1.7.0_15, but do in 1.6.0_27.

[Dzmitry Lazerka]

Of course, but then how to return Class<Alert<?>>?
AlertController.java:13: error: incompatible types
        return Alert.class;
                    ^
  required: Class<Alert<?>>
  found:    Class<Alert>
1 error

And it's not possible to cast Class<Alert> to Class<Alert<?>>, types are
incompatible.

-----
Best regards,
Dzmitry Lazerka


On Mon, Mar 11, 2013 at 10:05 AM, Maurizio Cimadamore <
maurizio.cimadamore at oracle.com> wrote:

>  On 11/03/13 17:02, Dzmitry Lazerka wrote:
>
> By the way, override wouldn't work, and I don't see any workaround:
>
>  AlertController.java:11: error: AlertController is not abstract and does
> not override abstract method getModelClass() in BaseController
> class AlertController extends BaseController<Alert<?>> {
> ^
> AlertController.java:12: error: getModelClass() in AlertController cannot
> override getModelClass() in BaseController
>     Class<Alert> getModelClass() {
>                  ^
>   return type Class<Alert> is not compatible with Class<Alert<?>>
>   where M is a type-variable:
>     M extends HasId<String> declared in class BaseController
> 2 errors
>
>   The return type in AlertController should match the one in the
> superclass - if you had Class<M> in the super class and M is Alert<?> in
> the subclass, the return type should be Class<Alert<?>>.
>
> Maurizio
>
>
> -----
> Best regards,
> Dzmitry Lazerka
>
>
> On Mon, Mar 11, 2013 at 3:41 AM, Maurizio Cimadamore <
> maurizio.cimadamore at oracle.com> wrote:
>
>>  Hi,
>> (cc'ing Alex)
>> if you do:
>>
>> class AlertController extends BaseController<Alert<Object>>
>>
>> or
>>
>> class AlertController extends BaseController<Alert<?>>
>>
>> The code and the override should compile.
>>
>> Said that, the behavior in JDK 7 is deliberate - the supertypes of a raw
>> type are all erased, which means the supertype of Alert is just HasId and
>> not HasId<String> as you would expect. This is the result of this fix:
>>
>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6559182
>>
>> Alex, can you comment on this? JLS section on raw types (4.8) only says
>> that the supertypes of a raw type are the erasure of such sypertypes - it
>> doesn't say this should be applied transitively. Also, Definition of type
>> erasure (4.6) doesn't say anything about supertypes.
>>
>> The rationale behind the fix for 6559182 is that all supertypes of a raw
>> type should be erased - which seems a fair assumption when looking at the
>> examples in 6559182 - however, should those two cases be treated
>> differently:
>>
>> Case A:
>>
>> class Foo<X> { }
>> class SubFoo<X> extends Foo<String> { }
>>
>> SubFoo sf = ...;
>>
>> Case B:
>>
>> class Foo<X> { }
>> class FooString extends Foo<String> { }
>> class SubFoo<X> extends FooString { }
>>
>> SubFoo sf = ...;
>>
>> In other words, is the fact that example (B) is using an intermediate
>> supertype that is not parameterized (but has parameterized supertype)
>> enough top warrant special treatment?
>>
>>
>> Maurizio
>>
>>
>> On 11/03/13 03:25, Dzmitry Lazerka wrote:
>>
>> Hi,
>>
>>  class HasId<I> {}
>> class HasStringId extends HasId<String> {}
>> class Alert<T extends /*Some*/Object> extends HasStringId {}
>> class BaseController<M extends HasId<String>> {
>>     // abstract Class<M> getModelClass();
>> }
>> class AlertController extends BaseController<Alert> { // error here
>>     // @Override Class<Alert> getModelClass() {
>>     //     return Alert.class;
>>     // }
>> }
>> compiles fine on OpenJDK6, but in OpenJDK7 gives:
>>
>>  Controller.java:50: error: type argument Alert is not within bounds of
>>     type-variable T
>> class Controller extends BaseController<Alert> {
>>                                         ^
>>   where T is a type-variable:
>>     T extends HasId<String> declared in class BaseController
>>
>>  Note that there's rawtype warning at line 50, because Alert must be
>> parameterized. If I do that, e.g. extends BaseController<Alert<Object>>,
>> code compiles. But I cannot do that, because I need to implement
>> getModelClass().
>>
>>  Ubuntu 12.04.
>>
>>  Is it a bug in 1.7.0_15? Can you suggest any workarounds?
>>
>> -----
>> Best regards,
>> Dzmitry Lazerka
>>
>>
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.openjdk.java.net/pipermail/compiler-dev/attachments/20130311/7f721d1c/attachment.html