abstract classes and interfaces

[kyle via Digitalmars-d-learn]

I'm attempting Markdown for the first time so forgive me if that 
doesn't go well. Consider the following:

```d
interface A
{
    bool broken();
}
abstract class B : A
{

}

class C : B
{

}

void main()
{
    import std.stdio;
    C test = new C();
    writeln(test);
}

```

DMD compiles this providing no notice that either B or C do not 
implement interface A. Is this how things are supposed to work? 
Thanks.