interface final members

[Joshua Reusch]

interface I {
	final int foo(I other, int a, int b) {
		return other.foo(a,b) + a*b;
	}
	int foo(int a, int b);
}

class A : I {
	int foo(int a, int b) {
		return a*b;
	}
}

void main() {
	A a = new A;

	a.foo(5,5);
	a.I.foo(a, 5,5);
	a.foo(a, 5,5); //line 22
}
---------
$ rdmd interface_final_test
interface_final_test.d(22): Error: function interface_final_test.A.foo 
(int a, int b) is not callable using argument types (A,int,int)
interface_final_test.d(22): Error: expected 2 arguments, not 3 for 
non-variadic function type int(int a, int b)
---------


Why do I need to write a.I.foo instead of a.foo to call the final method 
of the interface ?

Thank you, Joshua