core.sys.windows.com.ComObject apparently has wrongly laid out Vtable

[Carl Sturtivant]

On Thursday, 21 March 2024 at 03:48:04 UTC, Walter Bright wrote:
> On 3/20/2024 7:38 AM, Carl Sturtivant wrote:
>> So why isn't ComObject declared extern(C++) in druntime?
>
> Because COM objects need to follow the extern(Windows) calling 
> convention. It's a mistake to try to cast it to extern(C++).
>
> I didn't invent this. Microsoft did. COM was invented around 
> 1990 or so. It's cast in concrete.

I was hoping that the special treatment by the D language of 
IUnknown in core.sys.windows.com would apply to any class that 
inherited from it, even an extern(C++) class, so I could have my 
cake and eat it, and

```D
extern(C++) class ComObject : IUnknown { /* ... */ }
```
would produce a class with extern(Windows) calling and an 
extern(C++) COM compatible vtable.

This does compile. Does the extern(C++) remove the special 
treatment of IUnknown and revert the class to the wrong calling 
convention?