Function set_stopped

include/exec/async_scope.hpp:601–607

      }

      constexpr void set_stopped() noexcept
      {
        auto&            __state = *__state_;
        std::unique_lock __guard{__state.__mutex_};
        __save_completion(set_stopped_t());
        __dispatch_result_(__guard);
      }

      constexpr auto get_env() const noexcept -> __env_t<_Env> const &
      {