Clean up some suspicious code. There's no guarantee a constant of integer type is a ConstantInt, so it's not safe to just cast<> these to ConstantInt. (It could be a constant expression, for example) The code is shorter this way too :).

interface I {}
class A : I {}
class B : A {}

void main () {
    A a = new A;
    I i = a;

    assert(!cast(B)a);
    assert(!cast(B)i);
}