exec(sequence): fix environment query for a single-sender sequence

include/stdexec/__detail/__sequence.hpp

@@ -73,12 +73,14 @@ namespace STDEXEC
     template <class _Sender>
     struct __attrs<_Sender>
     {
-      template <class _Env2 = env_of_t<_Sender>, class _Query, class... _Args>
-        requires __queryable_with<_Env2, _Query, _Args...>
+      using _env_t = env_of_t<_Sender>;
+
+      template <class _Query, class... _Args>
+        requires __queryable_with<_env_t, _Query, _Args...>
       STDEXEC_ATTRIBUTE(nodiscard, always_inline, host, device)
-      constexpr auto operator()(_Query, _Args &&...__args) const
-        noexcept(__nothrow_queryable_with<_Env2, _Query, _Args...>)
-          -> __query_result_t<_Env2, _Query, _Args...>
+      constexpr auto query(_Query, _Args &&...__args) const
+        noexcept(__nothrow_queryable_with<_env_t, _Query, _Args...>)
+          -> __query_result_t<_env_t, _Query, _Args...>
       {
         return STDEXEC::get_env(__sndr_).query(_Query(), static_cast<_Args &&>(__args)...);
       }

test/stdexec/algos/adaptors/test_sequence.cpp

@@ -18,6 +18,7 @@
 #include <stdexec/execution.hpp>
 
 #include <exec/sequence.hpp>
+#include <exec/static_thread_pool.hpp>
 #include <test_common/receivers.hpp>
 #include <test_common/type_helpers.hpp>
 
@@ -187,3 +188,44 @@ TEST_CASE("sequence with sender with only first sender with throwing connect", "
   CHECK_THROWS(ex::connect(std::move(sndr), empty_recv::recv0{}));
 }
 #endif  // !STDEXEC_NO_STD_EXCEPTIONS()
+
+TEST_CASE("completion domain of a sequence of one sender", "[sequence]")
+{
+  exec::static_thread_pool pool{1};
+
+  unsigned short int value = 0;
+
+  auto sndr = exec::sequence(STDEXEC::schedule(pool.get_scheduler())
+                             | STDEXEC::then([&]() noexcept { value = 42; }));
+
+  static_assert(
+    std::same_as<
+      STDEXEC::__completion_domain_of_t<STDEXEC::set_value_t, decltype(sndr), STDEXEC::env<>>,
+      experimental::execution::_pool_::_static_thread_pool::domain>);
+
+  STDEXEC::sync_wait(std::move(sndr));
+
+  CHECK(value == 42);
+}
+
+TEST_CASE("completion domain of a sequence of two senders", "[sequence]")
+{
+  exec::static_thread_pool pool{1};
+
+  unsigned short int value_A = 0, value_B = 0;
+
+  auto sndr = exec::sequence(STDEXEC::schedule(pool.get_scheduler())
+                               | STDEXEC::then([&]() noexcept { value_A = 42; }),
+                             STDEXEC::schedule(pool.get_scheduler())
+                               | STDEXEC::then([&]() noexcept { value_B = 42; }));
+
+  static_assert(
+    std::same_as<
+      STDEXEC::__completion_domain_of_t<STDEXEC::set_value_t, decltype(sndr), STDEXEC::env<>>,
+      experimental::execution::_pool_::_static_thread_pool::domain>);
+
+  STDEXEC::sync_wait(std::move(sndr));
+
+  CHECK(value_A == 42);
+  CHECK(value_B == 42);
+}