#include <folly/Poly.h>
#include <iostream>
struct IDrawable {
  template <class Base>
  struct Interface : Base {
    void draw(std::ostream& out) const { folly::poly_call<0>(*this, out); }
  };
  template <class T>
  using Members = folly::PolyMembers<&T::draw>;
};
using drawable = folly::Poly<IDrawable>;
using drawableRef = folly::Poly< IDrawable const&>;
struct Square {
  void draw(std::ostream& out) const { out << "Square\n"; }
};
struct Circle {
  void draw(std::ostream& out) const { out << "Circle\n"; }
};
void f(drawable const& d) { d.draw(std::cout); }
void g(drawableRef  d) { d->draw(std::cout); }

int main()
{
  f(Square{});
  f(Circle{});
  Square s{};
  Circle c{};
  g(s);
  g(c);
  g(Square{});
  g(Circle{});
}