toString() through interface

[Steven Schveighoffer via Digitalmars-d-learn]

On Sat, 19 Apr 2014 20:45:50 -0400, Adam D. Ruppe  
<destructionator at gmail.com> wrote:

> On Sunday, 20 April 2014 at 00:35:30 UTC, David Held wrote:
>> Since all implementations of an interface must derive from Object
>
> That's not true. They can also come from IUnknown or a C++ interface.

This is also not true. Only interfaces derived from IUnknown point to a  
COM object. Only interfaces marked as extern(C++) can point to a C++  
object.

Any interface that is purely D MUST point at a D object that derives from  
Object, EVEN D-defined COM or C++ objects (the latter doesn't really  
exist).

His code should compile IMO.

>     cast(Object)(foo).toString();
>
> (cast(Object)foo).toString() might work
>
>
> This might return null tho if it is a non-D object through the interface!

As stated above, this is not possible.

-Steve