result_of -> invoke_result in pytorch/csprng/torchcsprng/csrc/kernels_body.inc

Summary: `result_of` is eliminated in C++20, so we use `invoke_result` instead

Reviewed By: palmje

Differential Revision: D57016781

fbshipit-source-id: cf7710d06a052d6d5a741de4e5bb8e56cc63cb0c

Author: ts-alchemist659op

torchcsprng/csrc/kernels_body.inc

@@ -15,7 +15,7 @@ at::Tensor key_tensor(size_t block_t_size, c10::optional<at::Generator> generato
   std::lock_guard<std::mutex> lock(generator->mutex());
   auto gen = at::check_generator<RNG>(generator);
   auto key = torch::empty({static_cast<signed long>(block_t_size)}, torch::kUInt8);
-  using random_t = typename std::result_of<decltype(&RNG::random)(RNG)>::type;
+  using random_t = typename std::invoke_result_t<decltype(&RNG::random), RNG>;
   constexpr size_t random_t_size = sizeof(random_t);
   for (size_t i = 0; i < block_t_size / random_t_size; i++) {
     const auto rand = gen->random();