//test case
import std.typecons;
class IA {}
class IB {}
class C : IB {
  IA a;
  mixin Proxy!a;

  public this() {
    a = new IA;
  }
}

void main() {
  C c = new C;
  assert(c !is null);

  IA a = cast(IA)c;
  assert(a !is null);

  IB b_ok = c;
  assert(b_ok !is null); //implicit cast works

  IB b_not_ok = cast(IB)c;
  assert(b_not_ok !is null); //assert fails on explicit cast.
}



//Proxy template always casts to Proxy'ied type:
 auto ref opCast(T, this X)() { return cast(T)a; }