fixes warnings and errors in clang16

include/exec/sequence/marbles.hpp

@@ -431,14 +431,15 @@ namespace exec {
         using __frame_t = typename _Clock::time_point;
         using __duration_t = typename _Clock::duration;
 
-        constexpr auto __make_span = []<std::size_t _LenB>(__mstring<_LenB>&& __string) noexcept {
-          return std::span<char>{__string.__what_, _LenB - 1};
-        };
+        constexpr auto __make_span =
+          []<std::size_t _LenB>(const __mstring<_LenB>& __string) noexcept {
+            return std::span<const char>{__string.__what_, _LenB - 1};
+          };
 
         std::vector<marble_t<_Clock>> __marbles;
         __frame_t __group_start_frame{-1ms};
         __frame_t __frame = __clock.now();
-        auto __whole = __make_span(std::move(__diagram));
+        auto __whole = __make_span(__diagram);
         auto __remaining = __whole;
         auto __consume_first = [&__remaining](std::size_t __skip) noexcept {
           __remaining = __remaining.subspan(__skip);
@@ -531,15 +532,18 @@ namespace exec {
                   && __all_digits) {
                   auto __to_consume = __suffix_begin - __remaining.begin();
                   long __duration = std::atol(__remaining.data());
-                  if (std::ranges::equal(
-                        __remaining.subspan(__to_consume, 3), __make_span("ms "_mstr))) {
+                  const auto __ms_str = "ms "_mstr;
+                  const auto __ms = __make_span(__ms_str);
+                  const auto __s_str = "s "_mstr;
+                  const auto __s = __make_span(__s_str);
+                  const auto __m_str = "m "_mstr;
+                  const auto __m = __make_span(__m_str);
+                  if (std::ranges::equal(__remaining.subspan(__to_consume, 3), __ms)) {
                     __to_consume += 2;
-                  } else if (std::ranges::equal(
-                               __remaining.subspan(__to_consume, 2), __make_span("s "_mstr))) {
+                  } else if (std::ranges::equal(__remaining.subspan(__to_consume, 2), __s)) {
                     __duration *= 1000;
                     __to_consume += 1;
-                  } else if (std::ranges::equal(
-                               __remaining.subspan(__to_consume, 2), __make_span("m "_mstr))) {
+                  } else if (std::ranges::equal(__remaining.subspan(__to_consume, 2), __m)) {
                     __duration = __duration * 1000 * 60;
                     __to_consume += 1;
                   } else {

include/exec/sequence/test_scheduler.hpp

@@ -826,7 +826,7 @@ namespace exec {
                  exec::schedule_at(__self.__context_->get_scheduler(), __marble.frame()),
                  static_cast<_Completion&&>(__completion)),
                stdexec::prop{stdexec::get_stop_token, __self.__stop_source_.get_token()})
-           | stdexec::upon_error([](auto&&) noexcept {}) | stdexec::upon_stopped([]() noexcept {})
+           | stdexec::upon_error([](auto&&) noexcept { }) | stdexec::upon_stopped([]() noexcept { })
            | stdexec::then([&__self, &__marble]() noexcept {
                // after each completion, update the __test_sequence_operation_part state
                STDEXEC_ASSERT(__self.__active_ops_ > 0);
@@ -869,10 +869,10 @@ namespace exec {
         decltype(__schedule_at(__self, __marble, stdexec::__declval<__next_t>()));
       using __end_sender_t = decltype(__schedule_at(__self, __marble, stdexec::just()));
       struct __next_sender_id {
-        using __t = __next_sender_t;
+        using __t [[maybe_unused]] = __next_sender_t;
       };
       struct __end_sender_id {
-        using __t = __end_sender_t;
+        using __t [[maybe_unused]] = __end_sender_t;
       };
 
       // WORKAROUND clang 19 would fail to compile the construction of the variant_sender.
@@ -919,14 +919,14 @@ namespace exec {
       using __id = __test_sequence;
       using sender_concept = exec::sequence_sender_t;
 
-      using marble_t = marble_t<test_clock>;
-      using marble_sender_t = marble_t::__marble_sender_t;
+      using __marble_t = marble_t<test_clock>;
+      using __marble_sender_t = __marble_t::__marble_sender_t;
 
       test_context* __context_;
-      std::vector<marble_t> __marbles_;
+      std::vector<__marble_t> __marbles_;
 
       template <stdexec::__decays_to<__test_sequence> _Self, class... _Env>
-      static auto get_item_types(_Self&&, _Env&&...) noexcept -> item_types<marble_sender_t> {
+      static auto get_item_types(_Self&&, _Env&&...) noexcept -> item_types<__marble_sender_t> {
         return {};
       }