cpp-descriptive-pointers/include/pointers/detail/get_ptr.hpp

#pragma once

namespace pointers { namespace detail {

  template <typename P, typename = void> struct get_ptr {
    decltype(std::declval<P>().get()) get(P const & ptr) const {
      return std::addressof(*ptr);
    }
  };

  template <typename T> struct get_ptr<std::weak_ptr<T>> {
    void get(std::weak_ptr<T> const & ptr) throw();
  };

  template <typename T> struct get_ptr<T *> {
    T * get(T * ptr) const { return ptr; }
  };

  template <typename P>
  struct get_ptr<P, typename std::enable_if<!std::is_void<decltype(
                        std::declval<P>().get())>::value>::type> {
    decltype(std::declval<P>().get()) get(P const & ptr) const {
      return ptr.get();
    }
  };

}}