> and your program code which treats this as impossible is just literally wrong That's fine though. The program that treats it as possible but fails to handle

> and your program code which treats this as impossible is just literally wrong That's fine though. The program that treats it as possible but fails to handle it in every possible spot is wrong too, but wrong in a completely unpredictable place, way and even number of times. It's freeing to start out assuming "title" can never be null. If it is, you get a quick failure at the very edge of your application where the data comes in. You make it nullable, and the compiler tells you all the places where you made the wrong assumption and now need a fix. Or even better yet, you give it a default value, even an empty string, and nothing more is required.