Type-safety is no silver bullet. For example, I'm perfectly capable of writing a type-safe application that's riddled with bugs. It's the kind of bugs that just sort of stop happening after a type-checker is introduced that are interesting. So what types of things can you expect after introducing a tool like Flow? I'll share three factors that I've experienced while learning Flow. The Type System section in the Flow docs goes into much more detail on this topic, available at https://flow.org/en/docs/lang/.