When you 'invoke' lua code, it creates coroutine

luprex/core/cpp/util.hpp

@@ -105,6 +105,9 @@ double distance_squared(double x1, double y1, double x2, double y2);
 // Return true if a world type is authoritative.
 bool world_type_authoritative(util::WorldType wt);
 
+// Make a LuaSourceVec with one element, for unit testing.
+LuaSourcePtr make_lua_source(const std::string &code);
+
 // Remove nullptrs from a vector of unique pointers.
 template<class T>
 void remove_nullptrs(std::vector<std::unique_ptr<T>> &vec) {