Method complete_

test/exec/asio/test_completion_token.cpp:65–71

    template <typename Tag, typename... Args>
    void complete_(Tag const & tag, Args&&... args) noexcept
    {
      CHECK(ptr_);
      CHECK(ptr_.use_count() == 1);
      tag(std::move(r_), std::forward<Args>(args)...);
      ptr_.reset();
    }
   public:
    using receiver_concept = receiver_tag;