add static asserts

fluent/Continuable.h

@@ -21,6 +21,11 @@
 
 #include "Callback.h"
 
+namespace detail
+{
+
+} // detail
+
 template <typename... _ATy>
 struct Continuable
 {
@@ -37,9 +42,9 @@ struct Continuable
         : _callback_insert(std::forward<_FTy>(callback_insert)) { }
 
     template <typename _CTy>
-    Continuable<_ATy...>& then(_CTy&&)
+    Continuable<_ATy...> then(_CTy&&)
     {
-        return *this;
+        return Continuable<_ATy...>();
     }
 };
 

fluent/functional_unwrap.hpp

@@ -160,6 +160,15 @@ namespace fu
     struct is_unwrappable
         : decltype(detail::test_unwrappable<Function...>(0)) { };
 
+    template<typename T>
+    struct requires_functional_constructible
+    {
+        static_assert(is_unwrappable<typename std::decay<T>::type>::value,
+            "Given type is not functional unwrappable, did you try to use a std::bind expression or a non functional type?");
+
+        typedef T type;
+    };
+
 } // fu
 
 #endif // _FUNCTIONAL_UNWRAP_HPP_

test.cpp

@@ -78,7 +78,7 @@ int main(int /*argc*/, char** /*argv*/)
 
     // Continuable<Callback<SpellCastResult>> spell
     CastSpell(63362)
-      .then([](SpellCastResult result)
+        .then([](SpellCastResult result)
         {
             return CastSpell(63362);
         })
@@ -95,6 +95,13 @@ int main(int /*argc*/, char** /*argv*/)
 
     });
 
+    std::vector<int> myvec;
+
+    typedef fu::requires_functional_constructible<std::function<void()>>::type test_assert1;
+    // typedef fu::requires_functional_constructible<std::vector<int>>::type test_assert2;
+
+    // auto cba2 = make_continuable(myvec);
+
     std::cout << "ok" << std::endl;
     return 0;
 }