Making illegal state unrepresentable

A couple of years ago, I wrote that The Builder pattern is a finite state machine! . A state machine consists of states and transitions between them. As a developer, I want to make illegal states unrepresentable, i.e. , users of my API can't create non-existent transitions. My hypothesis is that only a static typing system allows this at compile-time. Dynamic typing systems rely on runtime validation. In this blog post, I will show that it holds true, with a caveat. If your model has many combin