nyohoho unused variables

examples/source/tutorials/erase_demo.cpp

@@ -1,16 +1,30 @@
 #define SOL_ALL_SAFETIES_ON 1
 #include <sol/sol.hpp>
 
+#include <iostream>
+
 int main() {
 
 	sol::state lua;
 	lua["bark"] = 50;
 	sol::optional<int> x = lua["bark"];
 	// x will have a value
+	if (x) {
+		return -1;
+	}
+	else {
+		std::cout << "x has no value, as expected" << std::endl;
+	}
 
 	lua["bark"] = sol::lua_nil;
 	sol::optional<int> y = lua["bark"];
 	// y will not have a value
+	if (x) {
+		return -1;
+	}
+	else {
+		std::cout << "y has no value, as expected" << std::endl;
+	}
 
 	return 0;
 }