Default implementations in inherited interfaces

[Saurabh Das via Digitalmars-d-learn]

I have an interface A which declares a certain function. A second 
interface B inherits from A and wishes to provide a default 
implementation for that function. How can I achieve this? I'm 
facing an error when I try this:

interface A
{
     int func(int);
}

interface B : A
{
     final int func(int)
     {
         return 0;
     }
}

class C : B
{
}

rdmd it.d:
it.d(14): Error: class it.C interface function 'int func(int)' is 
not implemented

Thanks,
Saurabh