Write explanations of AST refactor in compiler series

06/main.cpp

@@ -36,6 +36,10 @@ void typecheck_program(
         pair.second->print(mgr, std::cout);
         std::cout << std::endl;
     }
+
+    for(auto& def : prog) {
+        def->resolve(mgr);
+    }
 }
 
 int main() {