metamethods for containers represented using userdata,

`#` == __len
`[key] = value` == __newindex
`key` == __index
are not working properly for some reason, will need to investigate more deeply to find out why
on bright side all tests pass including new tests added (for take/return std::function)
fixed some things forgot to change with addition of upvalue_t for clarity (see previous commit about userdata/lightuserdata vs upvalue)

sol/container.hpp

@@ -37,8 +37,8 @@ struct container {
 namespace stack {
 template<typename T>
 struct pusher<T, typename std::enable_if<has_begin_end<T>::value>::type> {
-    template <typename U>
-    static void push(lua_State *L, U&& t){
+    template<typename U = T, EnableIf<Not<has_key_value_pair<U>>> = 0>
+    static void push(lua_State* L, const T& cont) {
         typedef container<U> container_t;
         // todo: NEED to find a different way of handling this...
         static std::vector<std::shared_ptr<void>> classes{};
@@ -53,27 +53,13 @@ struct pusher<T, typename std::enable_if<has_begin_end<T>::value>::type> {
 
         container_t* c = static_cast<container_t*>(lua_newuserdata(L, sizeof(container_t)));
         std::allocator<container_t> alloc{};
-        alloc.construct(c, std::forward<U>(t));
+        alloc.construct(c, cont);
 
         auto&& meta = userdata_traits<T>::metatable;
         luaL_getmetatable(L, std::addressof(meta[0]));
         lua_setmetatable(L, -2);
     }
 
-    template<typename U = T, EnableIf<Not<has_key_value_pair<U>>> = 0>
-    static void push(lua_State* L, const T& cont) {
-        lua_createtable(L, cont.size(), 0);
-        unsigned index = 1;
-        for(auto&& i : cont) {
-            // push the index
-            pusher<unsigned>::push(L, index++);
-            // push the value
-            pusher<Unqualified<decltype(i)>>::push(L, i);
-            // set the table
-            lua_settable(L, -3);
-        }
-    }
-
     template<typename U = T, EnableIf<has_key_value_pair<U>> = 0>
     static void push(lua_State* L, const T& cont) {
         lua_createtable(L, cont.size(), 0);

sol/function_types.hpp

@@ -180,7 +180,7 @@ struct base_function {
     struct userdata {
         static int call(lua_State* L) {
             // Zero-based template parameter, but upvalues start at 1
-            return base_call(L, stack::get<lightuserdata_t>(L, i + 1));
+            return base_call(L, stack::get<upvalue_t>(L, i + 1));
         }
     };
 

sol/stack.hpp

@@ -286,7 +286,7 @@ template<typename T, typename... Args>
 inline void push(lua_State* L, T&& t, Args&&... args) {
     using swallow = char[];
     pusher<Unqualified<T>>{}.push(L, std::forward<T>(t));
-    void(swallow{'\0', (pusher<Unqualified<T>>{}.push(L, std::forward<Args>(args)), '\0')... });
+    void(swallow{'\0', (pusher<Unqualified<Args>>{}.push(L, std::forward<Args>(args)), '\0')... });
 }
 
 template<typename T, typename U = Unqualified<T>>

tests.cpp

@@ -14,6 +14,18 @@ void test_free_func2(std::function<int(int)> f, int arg1) {
         throw sol::error("failed function call!");
 }
 
+std::function<int()> makefn () {
+    auto fx = []() -> int {
+        return 0x1456789;
+    };
+    return fx;
+}
+
+void takefn ( std::function<int()> purr ) {
+    if (purr() != 0x1456789)
+        throw 0;
+}
+
 std::string free_function() {
     std::cout << "free_function()" << std::endl;
     return "test";
@@ -320,7 +332,7 @@ TEST_CASE("tables/functions_variables", "Check if tables and function calls work
             std::cout << "stateless lambda()" << std::endl;
             return "test";
         }
-);
+    );
     REQUIRE_NOTHROW(run_script(lua));
 
     lua.get<sol::table>("os").set_function("fun", &free_function);
@@ -388,6 +400,17 @@ TEST_CASE("functions/sol::function to std::function", "check if conversion to st
        );
 }
 
+TEST_CASE("functions/returning functions from C++ and getting in lua", "check to see if returning a functor and getting a functor from lua is possible") {
+    sol::state lua;
+    lua.open_libraries(sol::lib::base);
+
+    lua.set_function( "makefn", makefn );
+    lua.set_function( "takefn", takefn );
+    lua.script( "afx = makefn()\n"
+                "print(afx())\n"
+                "takefn(afx)\n" );
+}
+
 TEST_CASE("tables/operator[]", "Check if operator[] retrieval and setting works properly") {
     sol::state lua;
     lua.open_libraries(sol::lib::base);
@@ -558,7 +581,6 @@ TEST_CASE("tables/userdata utility derived", "userdata classes must play nice wh
     REQUIRE((lua.get<int>("dgn") == 7));
 }
 
-
 TEST_CASE("tables/self-referential userdata", "userdata classes must play nice when C++ object types are requested for C++ code") {
     sol::state lua;
     lua.open_libraries(sol::lib::base);