Function async_throw_from_completion

test/exec/asio/test_completion_token.cpp:229–242

  template <typename Executor, typename CompletionToken>
  decltype(auto) async_throw_from_completion(Executor const & ex, CompletionToken&& token)
  {
    using signature_type = void();
    return asio_impl::async_initiate<CompletionToken, signature_type>(
      [ex](auto h)
      {
        auto const assoc = asio_impl::get_associated_executor(h, ex);
        asio_impl::post(ex,
                        asio_impl::bind_executor(assoc,
                                                 [h = std::move(h)]()
                                                 { throw std::logic_error("Test"); }));
      },
      token);
  }

  TEST_CASE("When a completion handler invoked as part of a composed "
            "asynchronous operation throws that exception is captured and sent as a "