You would think that we'd have accounted for this earlier...

Fixes #405

examples/usertype_dynamic_getter_setter.cpp

@@ -61,7 +61,7 @@ struct vec {
 		return sol::object(L, sol::in_place, sol::lua_nil);
 	}
 
-	void setter(sol::stack_object key, sol::stack_object value, sol::this_state L) {
+	void setter(sol::stack_object key, sol::stack_object value, sol::this_state) {
 		// we use stack_object for the arguments because we know
 		// the values from Lua will remain on Lua's stack,
 		// so long we we don't mess with it

single/sol/sol.hpp

@@ -20,8 +20,8 @@
 // CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 // This file was generated with a script.
-// Generated 2017-05-15 14:41:13.667703 UTC
+// Generated 2017-05-16 10:11:15.504731 UTC
-// This header was generated with sol v2.17.3 (revision 7eccb58)
+// This header was generated with sol v2.17.3 (revision 34b81be)
 // https://github.com/ThePhD/sol2
 
 #ifndef SOL_SINGLE_INCLUDE_HPP
@@ -9357,11 +9357,16 @@ namespace sol {
 				stack::push(L, f);
 			}
 
-			template <typename Fx, typename... Args>
+			template <typename Fx, typename... Args, meta::disable<meta::any<std::is_base_of<reference, meta::unqualified_t<Fx>>, std::is_base_of<stack_reference, meta::unqualified_t<Fx>>>> = meta::enabler>
 			static void select(lua_State* L, Fx&& fx, Args&&... args) {
 				select_function(std::is_function<meta::unqualified_t<Fx>>(), L, std::forward<Fx>(fx), std::forward<Args>(args)...);
 			}
 
+			template <typename Fx, meta::enable<meta::any<std::is_base_of<reference, meta::unqualified_t<Fx>>, std::is_base_of<stack_reference, meta::unqualified_t<Fx>>>> = meta::enabler>
+			static void select(lua_State* L, Fx&& fx) {
+				stack::push(L, std::forward<Fx>(fx));
+			}
+
 			template <typename Fx, typename... Args>
 			static void set_fx(lua_State* L, Args&&... args) {
 				lua_CFunction freefunc = function_detail::call<meta::unqualified_t<Fx>, 2>;
@@ -9398,7 +9403,11 @@ namespace sol {
 
 		template<typename Signature>
 		struct pusher<std::function<Signature>> {
-			static int push(lua_State* L, std::function<Signature> fx) {
+			static int push(lua_State* L, const std::function<Signature>& fx) {
+				return pusher<function_sig<Signature>>{}.push(L, fx);
+			}
+
+			static int push(lua_State* L, std::function<Signature>&& fx) {
 				return pusher<function_sig<Signature>>{}.push(L, std::move(fx));
 			}
 		};

sol/function_types.hpp

@@ -190,11 +190,16 @@ namespace sol {
 				stack::push(L, f);
 			}
 
-			template <typename Fx, typename... Args>
+			template <typename Fx, typename... Args, meta::disable<meta::any<std::is_base_of<reference, meta::unqualified_t<Fx>>, std::is_base_of<stack_reference, meta::unqualified_t<Fx>>>> = meta::enabler>
 			static void select(lua_State* L, Fx&& fx, Args&&... args) {
 				select_function(std::is_function<meta::unqualified_t<Fx>>(), L, std::forward<Fx>(fx), std::forward<Args>(args)...);
 			}
 
+			template <typename Fx, meta::enable<meta::any<std::is_base_of<reference, meta::unqualified_t<Fx>>, std::is_base_of<stack_reference, meta::unqualified_t<Fx>>>> = meta::enabler>
+			static void select(lua_State* L, Fx&& fx) {
+				stack::push(L, std::forward<Fx>(fx));
+			}
+
 			template <typename Fx, typename... Args>
 			static void set_fx(lua_State* L, Args&&... args) {
 				lua_CFunction freefunc = function_detail::call<meta::unqualified_t<Fx>, 2>;
@@ -231,7 +236,11 @@ namespace sol {
 
 		template<typename Signature>
 		struct pusher<std::function<Signature>> {
-			static int push(lua_State* L, std::function<Signature> fx) {
+			static int push(lua_State* L, const std::function<Signature>& fx) {
+				return pusher<function_sig<Signature>>{}.push(L, fx);
+			}
+
+			static int push(lua_State* L, std::function<Signature>&& fx) {
 				return pusher<function_sig<Signature>>{}.push(L, std::move(fx));
 			}
 		};

test_functions.cpp

@@ -1064,3 +1064,74 @@ TEST_CASE("functions/overloaded-variadic", "make sure variadics work to some deg
 	REQUIRE(b == 3);
 	REQUIRE(c == 2.2);
 }
+
+TEST_CASE("functions/set_function-already-wrapped", "setting a function returned from Lua code that is already wrapped into a sol::function or similar") {
+	SECTION("test different types") {
+		sol::state lua;
+		lua.open_libraries(sol::lib::base);
+		sol::function fn = lua.script("return function() return 5 end");
+		sol::protected_function pfn = fn;
+		std::function<int()> sfn = fn;
+	
+		lua.set_function("test", fn);
+		lua.set_function("test2", pfn);
+		lua.set_function("test3", sfn);
+
+		REQUIRE_NOTHROW(lua.script("assert(type(test) == 'function')"));
+		REQUIRE_NOTHROW(lua.script("assert(test() ~= nil)"));
+		REQUIRE_NOTHROW(lua.script("assert(test() == 5)"));
+
+		REQUIRE_NOTHROW(lua.script("assert(type(test2) == 'function')"));
+		REQUIRE_NOTHROW(lua.script("assert(test2() ~= nil)"));
+		REQUIRE_NOTHROW(lua.script("assert(test2() == 5)"));
+
+		REQUIRE_NOTHROW(lua.script("assert(type(test3) == 'function')"));
+		REQUIRE_NOTHROW(lua.script("assert(test3() ~= nil)"));
+		REQUIRE_NOTHROW(lua.script("assert(test3() == 5)"));
+	}
+
+	SECTION("getting the value from C++") {
+		sol::state lua;
+		lua.open_libraries(sol::lib::base);
+		sol::function fn = lua.script("return function() return 5 end");
+
+		int result = fn();
+		REQUIRE(result == 5);
+	}
+
+	SECTION("setting the function directly") {
+		sol::state lua;
+		lua.open_libraries(sol::lib::base);
+		sol::function fn = lua.script("return function() return 5 end");
+
+		lua.set_function("test", fn);
+
+		REQUIRE_NOTHROW(lua.script("assert(type(test) == 'function')"));
+		REQUIRE_NOTHROW(lua.script("assert(test() ~= nil)"));
+		REQUIRE_NOTHROW(lua.script("assert(test() == 5)"));
+
+	}
+
+	SECTION("does the function actually get executed?") {
+		sol::state lua;
+		lua.open_libraries(sol::lib::base);
+
+		sol::function fn2 = lua.script("return function() print('this was executed') end");
+		lua.set_function("test", fn2);
+
+		REQUIRE_NOTHROW(lua.script("assert(type(test) == 'function')"));
+		REQUIRE_NOTHROW(lua.script("test()"));
+	}
+
+	SECTION("setting the function indirectly, with the return value cast explicitly") {
+		sol::state lua;
+		lua.open_libraries(sol::lib::base);
+		sol::function fn = lua.script("return function() return 5 end");
+
+		lua.set_function("test", [&fn]() { return fn.call<int>(); });
+
+		REQUIRE_NOTHROW(lua.script("assert(type(test) == 'function')"));
+		REQUIRE_NOTHROW(lua.script("assert(test() ~= nil)"));
+		REQUIRE_NOTHROW(lua.script("assert(test() == 5)"));
+	}
+}