Restriction on interface function types

[Steve Teale]

On Wednesday, 12 March 2014 at 13:12:20 UTC, Steven Schveighoffer 
wrote:
> On Wed, 12 Mar 2014 09:05:05 -0400, Steve Teale 
> <steve.teale at britseyeview.com> wrote:

> How is the compiler to build it's one copy of bad? Should x be 
> typed as A or B? Or something not even seen in this module that 
> could derive from I?
>
> -Steve

Let's take bad() away, and instead:

class A : I
{
    A myType() { return cast(A)null;}
    final void foo();
}

class B : I
{
    B myType() {return cast(B) null;}
    final void bar();
}

void main()
{
    I[] arr = [new A, new B];
    foreach(i; arr) { (cast(typeof(i.myType()) i).foo() }
}

myType() is a virtual function, so calling it through the 
interface type should get the correct version right?, and then 
the cast should cause a call to A or B.