Confused about interfaces in D

[Ary Borenszweig]

Bill Baxter escribió:
> On Thu, Oct 2, 2008 at 5:59 AM, Thomas Leonard <talex5+d at gmail.com> wrote:
>> Hi,
>>
>> I'm used to interfaces in Java, and I'm wondering why this doesn't work
>> in D:
>>
>>  interface Clock {}
>>
>>  class SystemClock : Clock {}
>>
>>  void main(string[] args) {
>>        Clock c = new SystemClock();
>>        c.toString();
>>  }
>>
>> It says:
>>
>>  $ dmd clock.d
>>  clock.d(7): Error: no property 'toString' for type 'clock.Clock'
>>
>> This compiles, though:
>>
>>        Clock c = new SystemClock();
>>        (cast(Object) c).toString();
>>
>> When is a "Clock" not an "Object"?
> 
> When it's derived from IUnknown, a special case put in to support COM
> interfaces on Win32.
> I've not heard anyone voice support for this particular design decision.
> I suppose it's very convenient if you happen to be a COM programmer,
> but I'm not sure why a vendor-specific technology like COM should get
> such special treatment in a language spec.
> 
> --bb

Better support a mostly unused specific case, than the broader general 
case, right?

:-(