Assume the following:

interface IFace {
  void foo();
  void bar();
}

abstract class A : IFace {
  override void foo() {}
}

class B : A {
  override void bar() {}
}

Now why this fails to compiler with the following message:


--->>>
function bar does not override any function, did you mean to override 'IFace.bar()'?
<<<---


Obviously, I meant that, since the abstract class A implements IFace, and B derives from A.

Do I need to declare IFace's unimplemented methods in A as abstract? If yes, why? Isn't that already obvious enough (any unimplemented virtual function is abstract)?

On 12/05/2017 11:23 PM, IM wrote:
> Assume the following:
> 
> interface IFace {
>    void foo();
>    void bar();
> }
> 
> abstract class A : IFace {
>    override void foo() {}
> }
> 
> class B : A {
>    override void bar() {}
> }
> 
> Now why this fails to compiler with the following message:
> 
> 
> --->>>
> function bar does not override any function, did you mean to override 'IFace.bar()'?
> <<<---
> 
> 
> Obviously, I meant that, since the abstract class A implements IFace, and B derives from A.
> 
> Do I need to declare IFace's unimplemented methods in A as abstract? If yes, why? Isn't that already obvious enough (any unimplemented virtual function is abstract)?

Just remove the override keywords in this case. No function is overriding any implementation here, they both implement an interface function. The fact that override can be used for A.foo can be seen as an inconsistency or a bug.

Ali

On Wednesday, 6 December 2017 at 07:23:29 UTC, IM wrote:
> Assume the following:
>
> interface IFace {
>   void foo();
>   void bar();
> }
>
> abstract class A : IFace {
>   override void foo() {}
> }
>
> class B : A {
>   override void bar() {}
> }
>
> Now why this fails to compiler with the following message:
>
>
> --->>>
> function bar does not override any function, did you mean to override 'IFace.bar()'?
> <<<---
>
>
> Obviously, I meant that, since the abstract class A implements IFace, and B derives from A.
>
> Do I need to declare IFace's unimplemented methods in A as abstract? If yes, why? Isn't that already obvious enough (any unimplemented virtual function is abstract)?

bar() is not a virtual function, but is defined in the interface IFace and thus you don't need to override it in B.

The same goes for foo() which I'd argue should have given same error.

What you possibly wanted to do is this:

interface IFace {
  void foo();
  void bar();
}

abstract class A : IFace {
  abstract void bar(); // All child classes must implement bar and override it

  abstract void foo(); // Since A implements IFace we must implement both bar() and foo()
                       // However it's an abstract class, so we can leave implementation
                       // up to the children.
}

class B : A {
  override void bar() {}

  override void foo() {}
}

On Wednesday, 6 December 2017 at 07:54:21 UTC, Ali Çehreli wrote:
> On 12/05/2017 11:23 PM, IM wrote:
>> [...]
>
> Just remove the override keywords in this case. No function is overriding any implementation here, they both implement an interface function. The fact that override can be used for A.foo can be seen as an inconsistency or a bug.
>
> Ali

I believe this is a bug, and a confusing one to be honest. Can you please help file one against the right owners? Thanks!

On 12/06/2017 03:01 PM, IM wrote:
> On Wednesday, 6 December 2017 at 07:54:21 UTC, Ali Çehreli wrote:
>> On 12/05/2017 11:23 PM, IM wrote:
>>> [...]
>>
>> Just remove the override keywords in this case. No function is
>> overriding any implementation here, they both implement an interface
>> function. The fact that override can be used for A.foo can be seen as
>> an inconsistency or a bug.
>>
>> Ali
>
> I believe this is a bug, and a confusing one to be honest. Can you
> please help file one against the right owners? Thanks!

There is no owners field when opening an issue. To get you started on the bug tracking system, please create this one yourself: :)

  https://issues.dlang.org/

Thank you,
Ali

On Wednesday, 6 December 2017 at 23:16:54 UTC, Ali Çehreli wrote:
> On 12/06/2017 03:01 PM, IM wrote:
> > On Wednesday, 6 December 2017 at 07:54:21 UTC, Ali Çehreli
> wrote:
> >> On 12/05/2017 11:23 PM, IM wrote:
> >>> [...]
> >>
> >> Just remove the override keywords in this case. No function
> is
> >> overriding any implementation here, they both implement an
> interface
> >> function. The fact that override can be used for A.foo can
> be seen as
> >> an inconsistency or a bug.
> >>
> >> Ali
> >
> > I believe this is a bug, and a confusing one to be honest.
> Can you
> > please help file one against the right owners? Thanks!
>
> There is no owners field when opening an issue. To get you started on the bug tracking system, please create this one yourself: :)
>
>   https://issues.dlang.org/
>
> Thank you,
> Ali

Done: https://issues.dlang.org/show_bug.cgi?id=18041. Thanks!