Inheritance

[Rémi Forax]

Mark Mahieu a écrit :
> Hi Zdeněk,
>
> I think the problem here is that the types { => Integer }, { => Number 
> } and { => Object } are all instances of the same generic interface 
> (javax.lang.function.O<R,X>) but with different type arguments, and 
> according to the JLS :
>
>
> /"A class may not at the same time be a subtype of two interface types 
> which are different invocations of the same generic interface 
> /_/(§9.1.2)/_ 
> <http://java.sun.com/docs/books/jls/third_edition/html/interfaces.html#78598>/, 
> or an invocation of a generic interface and a raw type naming that 
> same generic interface./
>
> /.../
>
> /This requirement was introduced in order to support translation by 
> type erasure /_/(§4.6)/_ 
> <http://java.sun.com/docs/books/jls/third_edition/html/typesValues.html#108979>/."/
>
> (From http://java.sun.com/docs/books/jls/third_edition/html/classes.html#8.1.5 
> )
>
>
> Regards,
Mark, this argument works for
interface Simple extends { => Integer }, { => Number }, { => Object } { }

but not for:
interface I1 extends { => Integer } { }
interface I2 extends { => Number } { }
interface I3 extends { => Object } { }
interface Simple extends I1, I2, I3 {}

because I1, I2 and I3 are reified types.

Neal, are you sure you want to allow a class or an interface to 
implements/extends
a function type ? Have you a real use case for that ?

I think it prevent to use JSR292's MethodHandle to implement function type.
>
> Mark
Rémi
>
>
> On 16 May 2008, at 08:32, tronicek at fel.cvut.cz 
> <mailto:tronicek at fel.cvut.cz> wrote:
>
>> Hi,
>>
>> this is compilable:
>>
>>     interface J1 {
>>         Integer invoke();
>>     }
>>
>>     interface J2 {
>>         Number invoke();
>>     }
>>
>>     interface J3 {
>>         Object invoke();
>>     }
>>
>>     interface J4 extends J1, J2, J3 { }
>>
>>     class C3 implements J1, J2, J3 {
>>         public Integer invoke() { return null; }
>>     }
>>
>>     class C4 implements J4 {
>>         public Integer invoke() { return null; }
>>     }
>>
>> and this is not:
>>
>>     interface I1 extends { => Integer } { }
>>
>>     interface I2 extends { => Number } { }
>>
>>     interface I3 extends { => Object } { }
>>
>>     interface I4 extends I1, I2, I3 { }
>>
>>     class C1 implements I1, I2, I3 {
>>         public Integer invoke() { return null; }
>>     }
>>
>>     class C2 implements I4 {
>>         public Integer invoke() { return null; }
>>     }
>>
>> But probably should be. As well as this:
>>
>>     interface Simple extends { => Integer }, { => Number }, { => 
>> Object } { }
>>
>> Zdenek
>> -- 
>> Zdenek Tronicek
>> Department of Computer Science and Engineering
>> Prague                   tel: +420 2 2435 7410
>> http://cs.felk.cvut.cz/~tronicek <http://cs.felk.cvut.cz/%7Etronicek>
>>
>>
>>
>>
>>
>>
>