clarify/fix std::visit compile time check

include/Common.h

@@ -132,6 +132,10 @@ private:
     static inline Version mVersion { 3, 9, 2 };
 };
 
+/// Used to static_assert in std::visit
+template<class>
+inline constexpr bool AlwaysFalseV = false;
+
 void SplitString(std::string const& str, const char delim, std::vector<std::string>& out);
 std::string LowerString(std::string str);
 

src/Common.cpp

@@ -378,7 +378,7 @@ std::ostream& operator<<(std::ostream& os, const TDetachedLuaValue& value) {
 
     std::visit([&os](auto&& arg) {
         using T = std::decay_t<decltype(arg)>;
-        if constexpr (std::is_same_v<T, std::vector<TDetachedLuaValue>>) {
+        if constexpr (std::is_same_v<T, TDetachedLuaValue::Array>) {
             size_t i = 0;
             for (auto val : arg) {
                 if (i > 0) {
@@ -386,7 +386,7 @@ std::ostream& operator<<(std::ostream& os, const TDetachedLuaValue& value) {
                 }
                 os << val;
             }
-        } else if constexpr (std::is_same_v<T, std::unordered_map<std::string, TDetachedLuaValue>>) {
+        } else if constexpr (std::is_same_v<T, TDetachedLuaValue::Object>) {
             size_t i = 0;
             for (auto [key, val] : arg) {
                 if (i > 0) {
@@ -406,7 +406,7 @@ std::ostream& operator<<(std::ostream& os, const TDetachedLuaValue& value) {
             // monostate means no result value
             os << "";
         else
-            static_assert(false, "non-exhaustive visitor!");
+            static_assert(AlwaysFalseV<T>, "non-exhaustive visitor!");
     },
         value.V);
 

src/TLuaEngine.cpp

@@ -570,7 +570,7 @@ sol::table TLuaEngine::StateThreadData::Lua_TriggerGlobalEvent(const std::string
                             // monostate means no result value
                             Result.set(i, sol::lua_nil_t());
                         else
-                            static_assert(false, "non-exhaustive visitor!");
+                            static_assert(AlwaysFalseV<T>, "non-exhaustive visitor!");
                     }, Snapshot.Result.V);
                 }
 
@@ -1259,7 +1259,7 @@ void TLuaEngine::StateThreadData::operator()() {
                             } else if constexpr (std::is_same_v<T, float>) {
                                 LuaArgs.push_back(sol::make_object(StateView, arg));
                             } else {
-                                static_assert(false, "unhandled variant");
+                                static_assert(AlwaysFalseV<T>, "unhandled variant");
                             }
                         }, Arg);
                     }