Allow non-default constructible types in static_thread_pool bulk cust…

…omization

include/exec/static_thread_pool.hpp

@@ -1193,7 +1193,7 @@ namespace exec {
           CvrefSender,
           env_of_t<Receiver>,
           __q<__decayed_std_tuple>,
-          __q<__std_variant>>;
+          __q<__nullable_std_variant>>;
 
       variant_t data_;
       static_thread_pool_& pool_;
@@ -1217,7 +1217,13 @@ namespace exec {
       template <class F>
       void apply(F f) {
         std::visit(
-          [&](auto& tupl) -> void { std::apply([&](auto&... args) -> void { f(args...); }, tupl); },
+          [&](auto& tupl) -> void {
+            if constexpr (same_as<__decay_t<decltype(tupl)>, std::monostate>) {
+              std::terminate();
+            } else {
+              std::apply([&](auto&... args) -> void { f(args...); }, tupl);
+            }
+          },
           data_);
       }
 

test/stdexec/algos/adaptors/test_bulk.cpp

@@ -19,6 +19,7 @@
 #include <stdexec/execution.hpp>
 #include <test_common/schedulers.hpp>
 #include <test_common/receivers.hpp>
+#include <test_common/senders.hpp>
 #include <test_common/type_helpers.hpp>
 #include <exec/static_thread_pool.hpp>
 
@@ -337,4 +338,18 @@ namespace {
       CHECK(actual != wrong);
     }
   }
+
+  TEST_CASE("default bulk works with non-default constructible types", "[adaptors][bulk]") {
+    ex::sender auto s = ex::just(non_default_constructible{42}) | ex::bulk(1, [](int, auto&) {});
+    ex::sync_wait(std::move(s));
+  }
+
+  TEST_CASE("static thread pool works with non-default constructible types", "[adaptors][bulk]") {
+    exec::static_thread_pool pool{4};
+    ex::scheduler auto sch = pool.get_scheduler();
+
+    ex::sender auto s = ex::just(non_default_constructible{42}) | ex::continues_on(sch)
+                      | ex::bulk(1, [](int, auto&) {});
+    ex::sync_wait(std::move(s));
+  }
 } // namespace

test/stdexec/algos/adaptors/test_schedule_from.cpp

@@ -18,6 +18,7 @@
 #include <stdexec/execution.hpp>
 #include <test_common/schedulers.hpp>
 #include <test_common/receivers.hpp>
+#include <test_common/senders.hpp>
 #include <test_common/type_helpers.hpp>
 #include <exec/any_sender_of.hpp>
 #include <exec/static_thread_pool.hpp>
@@ -112,19 +113,6 @@ namespace {
     REQUIRE(called);
   }
 
-  struct non_default_constructible {
-    int x;
-
-    non_default_constructible(int x)
-      : x(x) {
-    }
-
-    friend bool
-      operator==(non_default_constructible const & lhs, non_default_constructible const & rhs) {
-      return lhs.x == rhs.x;
-    }
-  };
-
   TEST_CASE(
     "schedule_from can accept non-default constructible types",
     "[adaptors][schedule_from]") {
@@ -249,4 +237,4 @@ namespace {
     auto op = ex::connect(std::move(snd), expect_value_receiver(3));
     ex::start(op);
   }
-} // namespace
+} // namespace

test/test_common/senders.hpp

@@ -168,4 +168,17 @@ namespace {
       return {self.condition_, std::forward<Receiver>(rcvr)};
     }
   };
+
+  struct non_default_constructible {
+    int x;
+
+    non_default_constructible(int x)
+      : x(x) {
+    }
+
+    friend bool
+      operator==(non_default_constructible const & lhs, non_default_constructible const & rhs) {
+      return lhs.x == rhs.x;
+    }
+  };
 } // namespace