Finish the async implementation

include/continuable/detail/operations/async.hpp

@@ -45,20 +45,24 @@ auto async(Callable&& callable, Args&&... args) {
       decltype(util::invoke(std::forward<decltype(callable)>(callable),
                             std::forward<decltype(args)>(args)...));
 
-  auto const hint =
-      decltype(base::decoration::invoker_of(identify<result_t>{}))::hint();
+  constexpr auto hint =
+      decltype(base::decoration::invoker_of(identity<result_t>{}))::hint();
 
   auto continuation = [callable = std::forward<decltype(callable)>(callable),
                        args = std::make_tuple(std::forward<decltype(args)>(
                            args)...)](auto&& promise) mutable {
-    // Select the invoker
-    auto invoker = base::decoration::invoker_of(identify<result_t>{});
 
-    traits::unpack([&](auto&&... args) {
-      // Invoke the promise through the dedicated invoker
-      invoker(std::move(callable), std::forward<decltype(promise)>(promise),
-              std::forward<decltype(args)>(args)...);
-    });
+    auto invoker = base::decoration::invoker_of(identity<result_t>{});
+
+    using promise_t = decltype(promise);
+
+    traits::unpack(
+        [&](auto&&... args) {
+          // Invoke the promise through the dedicated invoker
+          invoker(std::move(callable), std::forward<promise_t>(promise),
+                  std::forward<decltype(args)>(args)...);
+        },
+        std::move(args));
   };
 
   return base::attorney::create_from(std::move(continuation), //

include/continuable/operations/async.hpp

@@ -37,6 +37,29 @@
 namespace cti {
 /// \ingroup Operations
 /// \{
+
+/// Wraps the given callable inside a continuable_base such that it is
+/// invoked when the asynchronous result is requested to return the result.
+///
+/// The behaviour will be equal as when using make_ready_continuable together
+/// with continuable_base::then, but async is implemented in
+/// a more efficient way:
+/// ```cpp
+/// auto do_sth() {
+///   return async([] {
+///     do_sth_more();
+///     return 0;
+///   });
+/// }
+/// ```
+///
+/// \param callable The callable type which is invoked on request
+///
+/// \param args The arguments which are passed to the callable upon invocation.
+///
+/// \returns A continuable_base which asynchronous result type will
+///          be computated with the same rules as continuable_base::then .
+///
 template <typename Callable, typename... Args>
 auto async(Callable&& callable, Args&&... args) {
   return detail::operations::async(std::forward<Callable>(callable),