Add continuable::via to change the invocation chain to the given executor

include/continuable/continuable-base.hpp

@@ -434,6 +434,21 @@ public:
                                               std::forward<E>(executor));
   }
 
+  /// Returns a continuable_base which continues its invocation through the
+  /// given executor.
+  ///
+  /// \returns Returns a continuable_base of the same type.
+  ///
+  /// \since 4.2.0
+  template <typename E>
+  auto via(E&& executor) && {
+    return std::move(*this).next(
+        [](auto&&... args) {
+          return make_result(std::forward<decltype(args)>(args)...);
+        },
+        std::forward<E>(executor));
+  }
+
   /// Returns a continuable_base which will have its signature converted
   /// to the given Args.
   ///

test/unit-test/multi/test-continuable-base-executors.cpp

@@ -47,6 +47,26 @@ TYPED_TEST(single_dimension_tests, are_executor_dispatchable) {
   ASSERT_ASYNC_COMPLETION(std::move(chain));
 }
 
+TYPED_TEST(single_dimension_tests, are_executor_dispatchable_via) {
+  bool invoked = false;
+  auto executor = [&](auto&& work) {
+    // We can move the worker object
+    auto local = std::forward<decltype(work)>(work);
+    ASSERT_FALSE(invoked);
+    // We can invoke the worker object
+    std::move(local)();
+  };
+
+  auto chain = this->supply().via(executor).then([&] {
+    ASSERT_FALSE(invoked);
+    invoked = true;
+  });
+
+  ASSERT_ASYNC_COMPLETION(std::move(chain));
+
+  ASSERT_TRUE(invoked);
+}
+
 TYPED_TEST(single_dimension_tests, are_executor_exception_resolveable) {
   auto executor = [&](auto&& work) {
     std::forward<decltype(work)>(work).set_exception(supply_test_exception());