test.d:

    template Impl() {
        void foo() { printf("foo here\n"); }
    }

    interface Iface {
        void foo();
    }

    class Bar : Iface {
        mixin Impl;
    }

    int main() {
        Bar bar = new Bar();
        bar.foo();
        return 0;
    }


test.d(10): class Bar interface function Iface.foo is not implemented

 -- andy