What would be the consequence of implementing interfaces as fat pointers ?

[QAston]

On Sunday, 30 March 2014 at 00:57:25 UTC, deadalnix wrote:
> All is in the title.
>
> This is becoming increasingly the norm in new languages. It is 
> much better in term of performances (it avoid cascaded loads to 
> call methods, which can be really costly on modern CPUs), make 
> object themselves smaller.
>
> Would implementing them that way break D code ? What would be 
> the extent of the breakage ?

How hard would that be to implement? Hard data would be much 
better than performance guesses all over this thread.