Fixing some basic bugs MSVC didn't catch

sol/stack.hpp

@@ -107,7 +107,8 @@ inline bool get_helper<bool>(std::true_type, lua_State* L, int index) {
 }
 
 template<typename T>
-inline auto get_helper(std::false_type, lua_State* L, int index = -1) {
+inline auto get_helper(std::false_type, lua_State* L, int index = -1)
+-> decltype(get(types<T>(), L, index)) {
     // T is a class
     return get(types<T>(), L, index);
 }

sol/types.hpp

@@ -85,16 +85,6 @@ class function;
 class object;
 
 namespace detail {
-template<typename T>
-inline type arithmetic(std::true_type) {
-    return type::number;
-}
-
-template<typename T>
-inline type arithmetic(std::false_type) {
-    return usertype<T>(is_specialization_of<T, userdata>{});
-}
-
 template<typename T>
 inline type usertype(std::true_type) {
     return type::userdata;
@@ -104,6 +94,16 @@ template<typename T>
 inline type usertype(std::false_type) {
     return type::none;
 }
+
+template<typename T>
+inline type arithmetic(std::true_type) {
+    return type::number;
+}
+
+template<typename T>
+inline type arithmetic(std::false_type) {
+    return usertype<T>(is_specialization_of<T, userdata>{});
+}
 } // detail
 
 template<typename T>