Class throwing_copy

test/rrd/async_scope.cpp:71–79

  void thread(unsigned)
  {
    struct throwing_copy
    {
      throwing_copy() = default;

      throwing_copy(throwing_copy const &)
      {
        throw std::logic_error("");
      }
    };

    exec::single_thread_context ctx;
    ex::scheduler auto          sch = ctx.get_scheduler();