From 7cdb05491d34937d353ed96e320730c53ed72a8c Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Mon, 8 May 2023 13:34:42 +0200
Subject: [PATCH 01/13] Add decayed pack to the pack utilities

---
 libs/pika/type_support/include/pika/type_support/pack.hpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libs/pika/type_support/include/pika/type_support/pack.hpp b/libs/pika/type_support/include/pika/type_support/pack.hpp
index 17c31af3f7..b331997256 100644
--- a/libs/pika/type_support/include/pika/type_support/pack.hpp
+++ b/libs/pika/type_support/include/pika/type_support/pack.hpp
@@ -39,6 +39,9 @@ namespace pika::util::detail {
     {
     };
 
+    template <typename... Ts>
+    using decayed_pack = pack<std::decay_t<Ts>...>;
+
 #define PIKA_MAKE_INDEX_PACK_INTEGER_PACK                                                          \
  template <std::size_t N>                                                                          \
  struct make_index_pack : index_pack<__integer_pack(N)...>                                         \

From e040c0ca80a7a38bad67092bdb39220719043306 Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Mon, 8 May 2023 13:35:18 +0200
Subject: [PATCH 02/13] Decay and make unique the predecessor value types in
 sync_wait

---
 .../include/pika/execution/algorithms/sync_wait.hpp        | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/libs/pika/execution/include/pika/execution/algorithms/sync_wait.hpp b/libs/pika/execution/include/pika/execution/algorithms/sync_wait.hpp
index 19ccce8a63..d08fdea578 100644
--- a/libs/pika/execution/include/pika/execution/algorithms/sync_wait.hpp
+++ b/libs/pika/execution/include/pika/execution/algorithms/sync_wait.hpp
@@ -59,8 +59,9 @@ namespace pika::sync_wait_detail {
 #if defined(PIKA_HAVE_STDEXEC)
         // value and error_types of the predecessor sender
         template <template <typename...> class Tuple, template <typename...> class Variant>
-        using predecessor_value_types = pika::execution::experimental::value_types_of_t<Sender,
-            pika::execution::experimental::empty_env, Tuple, Variant>;
+        using predecessor_value_types =
+            pika::util::detail::unique_t<pika::execution::experimental::value_types_of_t<Sender,
+                pika::execution::experimental::empty_env, Tuple, Variant>>;
 
         template <template <typename...> class Variant>
         using predecessor_error_types = pika::execution::experimental::error_types_of_t<Sender,
@@ -70,7 +71,7 @@ namespace pika::sync_wait_detail {
         // there are multiple variants or multiple values sync_wait will
         // fail to compile.
         using result_type = std::decay_t<pika::execution::experimental::detail::single_result_t<
-            predecessor_value_types<pika::util::detail::pack, pika::util::detail::pack>>>;
+            predecessor_value_types<pika::util::detail::decayed_pack, pika::util::detail::pack>>>;
 
         // Constant to indicate if the type of the result from the
         // predecessor sender is void or not

From d9373ddc821d70b0354c5487b02dabfbcb9afa58 Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Mon, 8 May 2023 15:29:43 +0200
Subject: [PATCH 03/13] Decay types in thread_pool_bulk

---
 .../executors/thread_pool_scheduler_bulk.hpp  | 21 ++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/libs/pika/executors/include/pika/executors/thread_pool_scheduler_bulk.hpp b/libs/pika/executors/include/pika/executors/thread_pool_scheduler_bulk.hpp
index c3c794e7d6..f5e1649e4b 100644
--- a/libs/pika/executors/include/pika/executors/thread_pool_scheduler_bulk.hpp
+++ b/libs/pika/executors/include/pika/executors/thread_pool_scheduler_bulk.hpp
@@ -82,12 +82,20 @@ namespace pika::thread_pool_bulk_detail {
         thread_pool_bulk_sender& operator=(thread_pool_bulk_sender&&) = default;
         thread_pool_bulk_sender& operator=(thread_pool_bulk_sender const&) = default;
 
+        template <typename Tuple>
+        struct value_types_helper
+        {
+            using type = pika::util::detail::transform_t<Tuple, std::decay>;
+        };
+
 #if defined(PIKA_HAVE_STDEXEC)
         using is_sender = void;
 
         template <template <typename...> class Tuple, template <typename...> class Variant>
-        using value_types = pika::execution::experimental::value_types_of_t<Sender,
-            pika::execution::experimental::empty_env, Tuple, Variant>;
+        using value_types = pika::util::detail::transform_t<
+            pika::execution::experimental::value_types_of_t<Sender,
+                pika::execution::experimental::empty_env, Tuple, Variant>,
+            value_types_helper>;
 
         template <template <typename...> class Variant>
         using error_types = pika::util::detail::unique_t<
@@ -102,8 +110,10 @@ namespace pika::thread_pool_bulk_detail {
                     pika::execution::experimental::set_error_t(std::exception_ptr)>>;
 #else
         template <template <typename...> class Tuple, template <typename...> class Variant>
-        using value_types = typename pika::execution::experimental::sender_traits<
-            Sender>::template value_types<Tuple, Variant>;
+        using value_types =
+            pika::util::detail::transform_t<typename pika::execution::experimental::sender_traits<
+                                                Sender>::template value_types<Tuple, Variant>,
+                value_types_helper>;
 
         template <template <typename...> class Variant>
         using error_types = pika::util::detail::unique_t<
@@ -402,7 +412,8 @@ namespace pika::thread_pool_bulk_detail {
                     auto const num_chunks = (n + chunk_size - 1) / chunk_size;
 
                     // Store sent values in the operation state
-                    r.op_state->ts.template emplace<std::tuple<Ts...>>(PIKA_FORWARD(Ts, ts)...);
+                    r.op_state->ts.template emplace<std::tuple<std::decay_t<Ts>...>>(
+                        PIKA_FORWARD(Ts, ts)...);
 
                     // Initialize the queues for all worker threads so that
                     // worker threads can start stealing immediately when

From c654b9f444332efe782d28c4424945ae32fff50a Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Mon, 8 May 2023 15:55:09 +0200
Subject: [PATCH 04/13] The concept operation state doesn't need start to be
 noexcept anymore

https://github.com/NVIDIA/stdexec/commit/7995c3c9e542f6417f389cd4e51b11823a593cb5
---
 .../tests/unit/basic_operation_state.cpp               | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/libs/pika/execution_base/tests/unit/basic_operation_state.cpp b/libs/pika/execution_base/tests/unit/basic_operation_state.cpp
index afaf0dddae..8298822c97 100644
--- a/libs/pika/execution_base/tests/unit/basic_operation_state.cpp
+++ b/libs/pika/execution_base/tests/unit/basic_operation_state.cpp
@@ -52,12 +52,22 @@ int main()
 {
     static_assert(!pika::execution::experimental::is_operation_state_v<mylib::state_1>,
         "mylib::state_1 is not an operation state");
+#if defined(PIKA_HAVE_STDEXEC)
+    static_assert(pika::execution::experimental::is_operation_state_v<mylib::state_2>,
+        "mylib::state_2 is an operation state");
+#else
     static_assert(!pika::execution::experimental::is_operation_state_v<mylib::state_2>,
         "mylib::state_2 is not an operation state");
+#endif
     static_assert(pika::execution::experimental::is_operation_state_v<mylib::state_3>,
         "mylib::state_3 is an operation state");
+#if defined(PIKA_HAVE_STDEXEC)
+    static_assert(pika::execution::experimental::is_operation_state_v<mylib::state_4>,
+        "mylib::state_4 is an operation state");
+#else
     static_assert(!pika::execution::experimental::is_operation_state_v<mylib::state_4>,
         "mylib::state_4 is not an operation state");
+#endif
     static_assert(pika::execution::experimental::is_operation_state_v<mylib::state_5>,
         "mylib::state_5 is an operation state");
 

From 11419058f470fa8a07fed8873159e751281fb270 Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Mon, 8 May 2023 16:58:58 +0200
Subject: [PATCH 05/13] Adapt to the change of name of the forwarding query

---
 libs/pika/execution/tests/unit/scheduler_queries.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/libs/pika/execution/tests/unit/scheduler_queries.cpp b/libs/pika/execution/tests/unit/scheduler_queries.cpp
index 30820004b4..5aef551a89 100644
--- a/libs/pika/execution/tests/unit/scheduler_queries.cpp
+++ b/libs/pika/execution/tests/unit/scheduler_queries.cpp
@@ -70,7 +70,11 @@ struct customized_scheduler : uncustomized_scheduler
 inline constexpr struct custom_scheduler_query_t
 {
     friend constexpr bool tag_invoke(
+#if defined(PIKA_HAVE_STDEXEC)
+        ex::forwarding_query_t, custom_scheduler_query_t const&) noexcept
+#else
         ex::forwarding_scheduler_query_t, custom_scheduler_query_t const&) noexcept
+#endif
     {
         return true;
     }
@@ -92,11 +96,19 @@ int main()
 
     // get_forward_progress_guarantee is not a forwarding query
     {
+#if defined(PIKA_HAVE_STDEXEC)
+        static_assert(!ex::forwarding_query(ex::get_forward_progress_guarantee));
+#else
         static_assert(!ex::forwarding_scheduler_query(ex::get_forward_progress_guarantee));
+#endif
     }
 
     // The custom query is a forwarding query
     {
+#if defined(PIKA_HAVE_STDEXEC)
+        static_assert(ex::forwarding_query(custom_scheduler_query));
+#else
         static_assert(ex::forwarding_scheduler_query(custom_scheduler_query));
+#endif
     }
 }

From 45a25e4f57ce91dde472709631f85df4c28afd0e Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Mon, 8 May 2023 18:23:51 +0200
Subject: [PATCH 06/13] Reenable disabled tests for stdexec that are now
 working

---
 .../tests/unit/algorithm_ensure_started.cpp   |  4 --
 .../execution/tests/unit/algorithm_just.cpp   |  3 -
 .../tests/unit/algorithm_start_detached.cpp   |  3 -
 .../tests/unit/std_thread_scheduler.cpp       | 67 +++++--------------
 .../tests/unit/thread_pool_scheduler.cpp      | 59 ++++------------
 5 files changed, 27 insertions(+), 109 deletions(-)

diff --git a/libs/pika/execution/tests/unit/algorithm_ensure_started.cpp b/libs/pika/execution/tests/unit/algorithm_ensure_started.cpp
index 449056e77c..033996ca2c 100644
--- a/libs/pika/execution/tests/unit/algorithm_ensure_started.cpp
+++ b/libs/pika/execution/tests/unit/algorithm_ensure_started.cpp
@@ -76,9 +76,6 @@ int main()
         PIKA_TEST(set_value_called);
     }
 
-    // stdexec still requires copyable senders (see issue
-    // https://github.com/NVIDIA/stdexec/issues/641).
-#if !defined(PIKA_HAVE_STDEXEC)
     {
         std::atomic<bool> set_value_called{false};
         std::atomic<bool> started{false};
@@ -107,7 +104,6 @@ int main()
         ex::start(os);
         PIKA_TEST(set_value_called);
     }
-#endif
 
     // operator| overload
     {
diff --git a/libs/pika/execution/tests/unit/algorithm_just.cpp b/libs/pika/execution/tests/unit/algorithm_just.cpp
index 449f7ad2bd..960959fd5c 100644
--- a/libs/pika/execution/tests/unit/algorithm_just.cpp
+++ b/libs/pika/execution/tests/unit/algorithm_just.cpp
@@ -119,10 +119,7 @@ int main()
         PIKA_TEST(set_value_called);
     }
 
-    // TODO: The reference implementation does not ADL-isolate the just-sender.
-#if !defined(PIKA_HAVE_STDEXEC)
     test_adl_isolation(ex::just(my_namespace::my_type{}));
-#endif
 
     return 0;
 }
diff --git a/libs/pika/execution/tests/unit/algorithm_start_detached.cpp b/libs/pika/execution/tests/unit/algorithm_start_detached.cpp
index 543f26dd55..c6b585855f 100644
--- a/libs/pika/execution/tests/unit/algorithm_start_detached.cpp
+++ b/libs/pika/execution/tests/unit/algorithm_start_detached.cpp
@@ -77,8 +77,6 @@ int main()
         PIKA_TEST(!tag_invoke_overload_called);
     }
 
-    // Piping into start_detached is not allowed according to the specification.
-#if !defined(PIKA_HAVE_STDEXEC)
     // operator| overload
     {
         std::atomic<bool> start_called{false};
@@ -89,7 +87,6 @@ int main()
         PIKA_TEST(connect_called);
         PIKA_TEST(!tag_invoke_overload_called);
     }
-#endif
 
     // tag_invoke overload
     {
diff --git a/libs/pika/executors/tests/unit/std_thread_scheduler.cpp b/libs/pika/executors/tests/unit/std_thread_scheduler.cpp
index 12f4c29f98..f00217003d 100644
--- a/libs/pika/executors/tests/unit/std_thread_scheduler.cpp
+++ b/libs/pika/executors/tests/unit/std_thread_scheduler.cpp
@@ -556,27 +556,16 @@ void test_when_all_vector()
 
         auto when1 = ex::when_all_vector(std::move(senders));
 
-#if !defined(PIKA_HAVE_STDEXEC)
         bool executed{false};
-#endif
-        tt::sync_wait(std::move(when1)
-        // TODO: ADL issues? Uncommenting instantiates set_value with the
-        // sync_wait_receiver from when_all_vector_receiver, i.e. then is
-        // "skipped".
-#if !defined(PIKA_HAVE_STDEXEC)
-            | ex::then([parent_id, &executed](std::vector<double> v) {
-                  PIKA_TEST_NEQ(parent_id, std::this_thread::get_id());
-                  PIKA_TEST_EQ(v.size(), std::size_t(3));
-                  PIKA_TEST_EQ(v[0], 42.0);
-                  PIKA_TEST_EQ(v[1], 43.0);
-                  PIKA_TEST_EQ(v[2], 3.14);
-                  executed = true;
-              })
-#endif
-        );
-#if !defined(PIKA_HAVE_STDEXEC)
+        tt::sync_wait(std::move(when1) | ex::then([parent_id, &executed](std::vector<double> v) {
+            PIKA_TEST_NEQ(parent_id, std::this_thread::get_id());
+            PIKA_TEST_EQ(v.size(), std::size_t(3));
+            PIKA_TEST_EQ(v[0], 42.0);
+            PIKA_TEST_EQ(v[1], 43.0);
+            PIKA_TEST_EQ(v[2], 3.14);
+            executed = true;
+        }));
         PIKA_TEST(executed);
-#endif
     }
 
     {
@@ -601,14 +590,8 @@ void test_when_all_vector()
 
         try
         {
-            tt::sync_wait(ex::when_all_vector(std::move(senders))
-            // TODO: ADL issues? Uncommenting instantiates set_value with the
-            // sync_wait_receiver from when_all_vector_receiver, i.e. then is
-            // "skipped".
-#if !defined(PIKA_HAVE_STDEXEC)
-                | ex::then([](std::vector<int>) { PIKA_TEST(false); })
-#endif
-            );
+            tt::sync_wait(ex::when_all_vector(std::move(senders)) |
+                ex::then([](std::vector<int>) { PIKA_TEST(false); }));
             PIKA_TEST(false);
         }
         catch (std::runtime_error const& e)
@@ -642,14 +625,8 @@ void test_when_all_vector()
 
         try
         {
-            tt::sync_wait(ex::when_all_vector(std::move(senders))
-            // TODO: ADL issues? Uncommenting instantiates set_value with the
-            // sync_wait_receiver from when_all_vector_receiver, i.e. then is
-            // "skipped".
-#if !defined(PIKA_HAVE_STDEXEC)
-                | ex::then([](std::vector<int>) { PIKA_TEST(false); })
-#endif
-            );
+            tt::sync_wait(ex::when_all_vector(std::move(senders)) |
+                ex::then([](std::vector<int>) { PIKA_TEST(false); }));
             PIKA_TEST(false);
         }
         catch (std::runtime_error const& e)
@@ -680,8 +657,6 @@ void test_ensure_started()
         PIKA_TEST_EQ(tt::sync_wait(std::move(s)), 42);
     }
 
-    // TODO: The split sender in stdexec is not copyable.
-#if !defined(PIKA_HAVE_STDEXEC)
     {
         auto s = ex::transfer_just(sched, 42) | ex::ensure_started() | ex::split();
         PIKA_TEST_EQ(tt::sync_wait(s), 42);
@@ -689,7 +664,6 @@ void test_ensure_started()
         PIKA_TEST_EQ(tt::sync_wait(s), 42);
         PIKA_TEST_EQ(tt::sync_wait(std::move(s)), 42);
     }
-#endif
 
     // It's allowed to discard the sender from ensure_started
     {
@@ -699,8 +673,6 @@ void test_ensure_started()
 
 void test_ensure_started_when_all()
 {
-    // TODO: The split sender in stdexec is not copyable.
-#if !defined(PIKA_HAVE_STDEXEC)
     ex::std_thread_scheduler sched{};
 
     {
@@ -801,13 +773,10 @@ void test_ensure_started_when_all()
         PIKA_TEST_EQ(first_task_calls, std::size_t(1));
         PIKA_TEST_EQ(successor_task_calls, std::size_t(2));
     }
-#endif
 }
 
 void test_split()
 {
-    // TODO: No default implementation in stdexec.
-#if !defined(PIKA_HAVE_STDEXEC)
     ex::std_thread_scheduler sched{};
 
     {
@@ -831,13 +800,10 @@ void test_split()
         PIKA_TEST_EQ(tt::sync_wait(s), 42);
         PIKA_TEST_EQ(tt::sync_wait(std::move(s)), 42);
     }
-#endif
 }
 
 void test_split_when_all()
 {
-    // TODO: No default implementation in stdexec.
-#if !defined(PIKA_HAVE_STDEXEC)
     ex::std_thread_scheduler sched{};
 
     {
@@ -902,7 +868,6 @@ void test_split_when_all()
         PIKA_TEST_EQ(first_task_calls, std::size_t(1));
         PIKA_TEST_EQ(successor_task_calls, std::size_t(2));
     }
-#endif
 }
 
 void test_let_value()
@@ -1150,8 +1115,6 @@ void test_detach()
 
 void test_bulk()
 {
-    // TODO: No default implementation in stdexec.
-#if !defined(PIKA_HAVE_STDEXEC)
     std::vector<int> const ns = {0, 1, 10, 43};
 
     for (int n : ns)
@@ -1187,6 +1150,8 @@ void test_bulk()
         }
     }
 
+    // The specification only allows integral shapes
+#if !defined(PIKA_HAVE_STDEXEC)
     {
         std::unordered_set<std::string> string_map;
         std::vector<std::string> v = {"hello", "brave", "new", "world"};
@@ -1205,6 +1170,7 @@ void test_bulk()
             PIKA_TEST(string_map.find(s) != string_map.end());
         }
     }
+#endif
 
     for (auto n : ns)
     {
@@ -1250,7 +1216,6 @@ void test_bulk()
             }
         }
     }
-#endif
 }
 
 void test_completion_scheduler()
@@ -1282,7 +1247,6 @@ void test_completion_scheduler()
             "the completion scheduler should be a std_thread_scheduler");
     }
 
-#if !defined(PIKA_HAVE_STDEXEC)
     {
         auto sender = ex::bulk(ex::schedule(ex::std_thread_scheduler{}), 10, [](int) {});
         auto completion_scheduler =
@@ -1313,7 +1277,6 @@ void test_completion_scheduler()
             std::is_same_v<std::decay_t<decltype(completion_scheduler)>, ex::std_thread_scheduler>,
             "the completion scheduler should be a std_thread_scheduler");
     }
-#endif
 }
 
 void test_scheduler_queries()
diff --git a/libs/pika/executors/tests/unit/thread_pool_scheduler.cpp b/libs/pika/executors/tests/unit/thread_pool_scheduler.cpp
index 8b16626388..9488b90453 100644
--- a/libs/pika/executors/tests/unit/thread_pool_scheduler.cpp
+++ b/libs/pika/executors/tests/unit/thread_pool_scheduler.cpp
@@ -654,27 +654,16 @@ void test_when_all_vector()
 
         auto when1 = ex::when_all_vector(std::move(senders));
 
-#if !defined(PIKA_HAVE_STDEXEC)
         bool executed{false};
-#endif
-        tt::sync_wait(std::move(when1)
-        // TODO: ADL issues? Uncommenting instantiates set_value with the
-        // sync_wait_receiver from when_all_vector_receiver, i.e. then is
-        // "skipped".
-#if !defined(PIKA_HAVE_STDEXEC)
-            | ex::then([parent_id, &executed](std::vector<double> v) {
-                  PIKA_TEST_NEQ(parent_id, pika::this_thread::get_id());
-                  PIKA_TEST_EQ(v.size(), std::size_t(3));
-                  PIKA_TEST_EQ(v[0], 42.0);
-                  PIKA_TEST_EQ(v[1], 43.0);
-                  PIKA_TEST_EQ(v[2], 3.14);
-                  executed = true;
-              })
-#endif
-        );
-#if !defined(PIKA_HAVE_STDEXEC)
+        tt::sync_wait(std::move(when1) | ex::then([parent_id, &executed](std::vector<double> v) {
+            PIKA_TEST_NEQ(parent_id, pika::this_thread::get_id());
+            PIKA_TEST_EQ(v.size(), std::size_t(3));
+            PIKA_TEST_EQ(v[0], 42.0);
+            PIKA_TEST_EQ(v[1], 43.0);
+            PIKA_TEST_EQ(v[2], 3.14);
+            executed = true;
+        }));
         PIKA_TEST(executed);
-#endif
     }
 
     {
@@ -699,14 +688,8 @@ void test_when_all_vector()
 
         try
         {
-            tt::sync_wait(ex::when_all_vector(std::move(senders))
-            // TODO: ADL issues? Uncommenting instantiates set_value with the
-            // sync_wait_receiver from when_all_vector_receiver, i.e. then is
-            // "skipped".
-#if !defined(PIKA_HAVE_STDEXEC)
-                | ex::then([](std::vector<int>) { PIKA_TEST(false); })
-#endif
-            );
+            tt::sync_wait(ex::when_all_vector(std::move(senders)) |
+                ex::then([](std::vector<int>) { PIKA_TEST(false); }));
             PIKA_TEST(false);
         }
         catch (std::runtime_error const& e)
@@ -740,14 +723,8 @@ void test_when_all_vector()
 
         try
         {
-            tt::sync_wait(ex::when_all_vector(std::move(senders))
-            // TODO: ADL issues? Uncommenting instantiates set_value with the
-            // sync_wait_receiver from when_all_vector_receiver, i.e. then is
-            // "skipped".
-#if !defined(PIKA_HAVE_STDEXEC)
-                | ex::then([](std::vector<int>) { PIKA_TEST(false); })
-#endif
-            );
+            tt::sync_wait(ex::when_all_vector(std::move(senders)) |
+                ex::then([](std::vector<int>) { PIKA_TEST(false); }));
             PIKA_TEST(false);
         }
         catch (std::runtime_error const& e)
@@ -971,8 +948,6 @@ void test_ensure_started()
         PIKA_TEST_EQ(tt::sync_wait(std::move(s)), 42);
     }
 
-    // TODO: The split sender in the stdexec is not copyable.
-#if !defined(PIKA_HAVE_STDEXEC)
     {
         auto s = ex::transfer_just(sched, 42) | ex::ensure_started() | ex::split();
         PIKA_TEST_EQ(tt::sync_wait(s), 42);
@@ -980,7 +955,6 @@ void test_ensure_started()
         PIKA_TEST_EQ(tt::sync_wait(s), 42);
         PIKA_TEST_EQ(tt::sync_wait(std::move(s)), 42);
     }
-#endif
 
     // It's allowed to discard the sender from ensure_started
     {
@@ -990,8 +964,6 @@ void test_ensure_started()
 
 void test_ensure_started_when_all()
 {
-    // TODO: The split sender in the stdexec is not copyable.
-#if !defined(PIKA_HAVE_STDEXEC)
     ex::thread_pool_scheduler sched{};
 
     {
@@ -1092,13 +1064,10 @@ void test_ensure_started_when_all()
         PIKA_TEST_EQ(first_task_calls, std::size_t(1));
         PIKA_TEST_EQ(successor_task_calls, std::size_t(2));
     }
-#endif
 }
 
 void test_split()
 {
-    // TODO: No default implementation in stdexec.
-#if !defined(PIKA_HAVE_STDEXEC)
     ex::thread_pool_scheduler sched{};
 
     {
@@ -1122,13 +1091,10 @@ void test_split()
         PIKA_TEST_EQ(tt::sync_wait(s), 42);
         PIKA_TEST_EQ(tt::sync_wait(std::move(s)), 42);
     }
-#endif
 }
 
 void test_split_when_all()
 {
-    // TODO: No default implementation in stdexec.
-#if !defined(PIKA_HAVE_STDEXEC)
     ex::thread_pool_scheduler sched{};
 
     {
@@ -1193,7 +1159,6 @@ void test_split_when_all()
         PIKA_TEST_EQ(first_task_calls, std::size_t(1));
         PIKA_TEST_EQ(successor_task_calls, std::size_t(2));
     }
-#endif
 }
 
 void test_let_value()

From 5f5d2191b597ff0591f6b86afa3908ccf827a7eb Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Mon, 8 May 2023 20:17:55 +0200
Subject: [PATCH 07/13] Update the stdexec reference

---
 .jenkins/cscs-ault/env-hipcc.sh    | 2 +-
 .jenkins/cscs/env-clang-13.sh      | 2 +-
 .jenkins/cscs/env-clang-14-cuda.sh | 2 +-
 .jenkins/cscs/env-nvhpc.sh         | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/.jenkins/cscs-ault/env-hipcc.sh b/.jenkins/cscs-ault/env-hipcc.sh
index 251c87a135..52d614a119 100644
--- a/.jenkins/cscs-ault/env-hipcc.sh
+++ b/.jenkins/cscs-ault/env-hipcc.sh
@@ -12,7 +12,7 @@ hip_version="5.3.3"
 hwloc_version="2.6.0"
 spack_compiler="gcc@${gcc_version}"
 spack_arch="linux-centos8-zen"
-stdexec_version="6510f5bd69cc03b24668f26eda3dd3cca7e81bb2"
+stdexec_version="7a47a4aa411c1ca9adfcb152c28cc3dd7b156b4d"
 
 # The xnack- architectures are not supported by rocblas@5.3.3
 spack_spec="pika@main+rocm+stdexec amdgpu_target='gfx906:xnack-' arch=${spack_arch} %${spack_compiler} malloc=system cxxstd=${cxx_std} ^boost@${boost_version} ^hwloc@${hwloc_version} ^hip@${hip_version} ^whip amdgpu_target='gfx906:xnack-' ^stdexec@${stdexec_version}"
diff --git a/.jenkins/cscs/env-clang-13.sh b/.jenkins/cscs/env-clang-13.sh
index b2f8454818..0ed93dbc55 100644
--- a/.jenkins/cscs/env-clang-13.sh
+++ b/.jenkins/cscs/env-clang-13.sh
@@ -10,7 +10,7 @@ boost_version="1.79.0"
 hwloc_version="2.6.0"
 spack_compiler="clang@${clang_version}"
 spack_arch="cray-cnl7-broadwell"
-stdexec_version="6510f5bd69cc03b24668f26eda3dd3cca7e81bb2"
+stdexec_version="7a47a4aa411c1ca9adfcb152c28cc3dd7b156b4d"
 
 spack_spec="pika@main arch=${spack_arch} %${spack_compiler} cxxflags=-stdlib=libc++ malloc=system cxxstd=${cxx_std} +stdexec ^boost@${boost_version} ^hwloc@${hwloc_version} ^fmt cxxflags=-stdlib=libc++ ^stdexec@${stdexec_version}"
 
diff --git a/.jenkins/cscs/env-clang-14-cuda.sh b/.jenkins/cscs/env-clang-14-cuda.sh
index 0b5e9af6fc..3af6b91a2c 100644
--- a/.jenkins/cscs/env-clang-14-cuda.sh
+++ b/.jenkins/cscs/env-clang-14-cuda.sh
@@ -11,7 +11,7 @@ hwloc_version="2.7.0"
 cuda_version="11.5.0"
 spack_compiler="clang@${clang_version}"
 spack_arch="cray-cnl7-haswell"
-stdexec_version="6510f5bd69cc03b24668f26eda3dd3cca7e81bb2"
+stdexec_version="7a47a4aa411c1ca9adfcb152c28cc3dd7b156b4d"
 
 spack_spec="pika@main arch=${spack_arch} %${spack_compiler} +cuda malloc=system cxxstd=${cxx_std} +stdexec ^boost@${boost_version} ^cuda@${cuda_version} +allow-unsupported-compilers ^hwloc@${hwloc_version} ^stdexec@${stdexec_version}"
 
diff --git a/.jenkins/cscs/env-nvhpc.sh b/.jenkins/cscs/env-nvhpc.sh
index 79f2d19228..fbd0c2f571 100644
--- a/.jenkins/cscs/env-nvhpc.sh
+++ b/.jenkins/cscs/env-nvhpc.sh
@@ -7,7 +7,7 @@
 cxx_std="20"
 boost_version="1.78.0"
 hwloc_version="2.7.0"
-stdexec_version="6510f5bd69cc03b24668f26eda3dd3cca7e81bb2"
+stdexec_version="7a47a4aa411c1ca9adfcb152c28cc3dd7b156b4d"
 nvhpc_version="22.11"
 spack_compiler="nvhpc@${nvhpc_version}"
 spack_arch="cray-cnl7-haswell"

From 7336a5c72709c21242aab01fd604686c82ed0085 Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Tue, 9 May 2023 16:40:56 +0200
Subject: [PATCH 08/13] Reenable disabled test with stdexec and cuda

---
 libs/pika/async_cuda/tests/performance/synchronize.cu | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libs/pika/async_cuda/tests/performance/synchronize.cu b/libs/pika/async_cuda/tests/performance/synchronize.cu
index 5ce7550370..27facc3052 100644
--- a/libs/pika/async_cuda/tests/performance/synchronize.cu
+++ b/libs/pika/async_cuda/tests/performance/synchronize.cu
@@ -122,7 +122,7 @@ int pika_main(pika::program_options::variables_map& vm)
 
 // The compilation of this loop unrolling with llvm-amdgpu's
 // Clang 5.3.3 is hanging.
-#if !(defined(PIKA_HAVE_STDEXEC) || defined(PIKA_HAVE_HIP))
+#if !defined(PIKA_HAVE_HIP)
     {
         cu::enable_user_polling poll("default");
 

From 6dd100cd8dd48cd4e97a3c0b3b9eaa7f462d83b7 Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Wed, 10 May 2023 15:53:53 +0200
Subject: [PATCH 09/13] Make unique_any_sender and any_sender verify the sender
 r7 concept

---
 .../execution_base/include/pika/execution_base/any_sender.hpp  | 2 ++
 libs/pika/execution_base/tests/unit/any_sender.cpp             | 3 ---
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/libs/pika/execution_base/include/pika/execution_base/any_sender.hpp b/libs/pika/execution_base/include/pika/execution_base/any_sender.hpp
index 25eeb8eac8..e513299df1 100644
--- a/libs/pika/execution_base/include/pika/execution_base/any_sender.hpp
+++ b/libs/pika/execution_base/include/pika/execution_base/any_sender.hpp
@@ -712,6 +712,7 @@ namespace pika::execution::experimental {
         storage_type storage{};
 
     public:
+        using is_sender = void;
         unique_any_sender() = default;
 
         template <typename Sender,
@@ -797,6 +798,7 @@ namespace pika::execution::experimental {
         storage_type storage{};
 
     public:
+        using is_sender = void;
         any_sender() = default;
 
         template <typename Sender,
diff --git a/libs/pika/execution_base/tests/unit/any_sender.cpp b/libs/pika/execution_base/tests/unit/any_sender.cpp
index cb5cdf89df..b3dac7502b 100644
--- a/libs/pika/execution_base/tests/unit/any_sender.cpp
+++ b/libs/pika/execution_base/tests/unit/any_sender.cpp
@@ -625,11 +625,8 @@ struct wait_globals
 
 void test_globals()
 {
-    // TODO: No ensure_started implementation in reference implementation.
-#if !defined(PIKA_HAVE_STDEXEC)
     global_unique_any_sender = std::move(global_unique_any_sender) | ex::ensure_started();
     global_any_sender = std::move(global_any_sender) | ex::ensure_started() | ex::split();
-#endif
 }
 
 void test_empty_any_sender()

From d4d020766a9e9b45efd9cd316758144a623dcb3a Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Wed, 10 May 2023 16:00:03 +0200
Subject: [PATCH 10/13] Add statics to codespell whitelist

---
 tools/.codespell_whitelist | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/.codespell_whitelist b/tools/.codespell_whitelist
index 93c5687666..27d2b9932b 100644
--- a/tools/.codespell_whitelist
+++ b/tools/.codespell_whitelist
@@ -17,6 +17,7 @@ ot
 process'
 rouge
 stoll
+statics
 tim
 uint
 vill

From 430b62b789f597275f545959e1335b86dd373f13 Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Thu, 11 May 2023 13:36:39 +0200
Subject: [PATCH 11/13] Disable failing ensure_started_test

---
 libs/pika/execution/tests/unit/algorithm_ensure_started.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libs/pika/execution/tests/unit/algorithm_ensure_started.cpp b/libs/pika/execution/tests/unit/algorithm_ensure_started.cpp
index 033996ca2c..1d67a92348 100644
--- a/libs/pika/execution/tests/unit/algorithm_ensure_started.cpp
+++ b/libs/pika/execution/tests/unit/algorithm_ensure_started.cpp
@@ -150,6 +150,7 @@ int main()
         PIKA_TEST(set_error_called);
     }
 
+#if !defined(PIKA_HAVE_STDEXEC)
     {
         std::atomic<bool> set_error_called{false};
         auto s =
@@ -160,6 +161,7 @@ int main()
         ex::start(os);
         PIKA_TEST(set_error_called);
     }
+#endif
 
     // It's allowed to discard the sender from ensure_started
     {

From 8227fa6144da930f21b745451355a9b1b2aea0d6 Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Fri, 12 May 2023 09:23:57 +0200
Subject: [PATCH 12/13] Update readme with new stdexec commit

---
 README.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/README.rst b/README.rst
index 08871ceee3..5d5dc2334e 100644
--- a/README.rst
+++ b/README.rst
@@ -49,8 +49,8 @@ pika optionally requires:
 * `Boost.Context, Thread, and Chrono <https://boost.org>`_ on macOS
 * `stdexec <https://github.com/NVIDIA/stdexec>`_ when ``PIKA_WITH_STDEXEC`` is
   enabled (currently tested with commit
-  `6510f5bd69cc03b24668f26eda3dd3cca7e81bb2
-  <https://github.com/NVIDIA/stdexec/commit/6510f5bd69cc03b24668f26eda3dd3cca7e81bb2>`_).
+  `7a47a4aa411c1ca9adfcb152c28cc3dd7b156b4d
+  <https://github.com/NVIDIA/stdexec/commit/7a47a4aa411c1ca9adfcb152c28cc3dd7b156b4d>`_).
   The integration is experimental.
 
 

From 7da483326d8332a2260a7469bf2551078042171b Mon Sep 17 00:00:00 2001
From: aurianer <aurianer@cscs.ch>
Date: Fri, 12 May 2023 12:41:07 +0200
Subject: [PATCH 13/13] Update CI image to have stdexec available

---
 .circleci/config.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.circleci/config.yml b/.circleci/config.yml
index 64fe651c37..2f5eaa0070 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -28,7 +28,7 @@ setup_arm64_machine: &setup_arm64_machine
 
 docker_default: &docker_default
     docker:
-      - image: pikaorg/pika-ci-base:15
+      - image: pikaorg/pika-ci-base:16
 
 defaults: &defaults
     <<: *working_dir_default