The interface's 'in' contract passes if it makes a virtual function call

[Ali Çehreli via Digitalmars-d-learn]

On 11/04/2014 12:41 PM, Steven Schveighoffer wrote:

 > Yep. I debugged it. It's calling toHash instead.

Yeah, you were spot on. :) I did a different experiment. I added a 
number of functions to the interface (before virtualCheck()) and 
implementations to the class:

interface I
{
// ...

     bool a();
     bool b();
     bool c();
     bool d();

     bool virtualCheck();
}


class C : I
{
// ...

     bool a() { return false; }
     bool b() { return false; }
     bool c() { return false; }
     bool d() { return false; }
}

Adding only a() calls C's precondition unconditionally (because it 
pushes virtualCheck() to the next slot in vtbl.)

Adding a() and b() has the same effect.

Adding a(), b(), and c() prints I.foo.in indefinitely. :)

Finally, adding a(), b(), c(), and d() seems to bring the expected 
behavior. :)

Ali