Function get_allocator

include/exec/static_thread_pool.hpp:1571–1581

    {
      template <class Rcvr>
      auto get_allocator(Rcvr const & rcvr)
      {
        if constexpr (__callable<get_allocator_t, env_of_t<Rcvr>>)
        {
          return STDEXEC::get_allocator(STDEXEC::get_env(rcvr));
        }
        else
        {
          return std::allocator<char>{};
        }
      }

      template <class Receiver>
      using allocator_of_t = decltype(get_allocator(__declval<Receiver>()));