I’m absolutely for this change 
Most people focus on library code, but I think it’s also important inside a single codebase, maintained by one team. Currently, we have no language support for setting up boundaries and establishing clear interfaces between different parts of the application, which can lead to issues with maintainability.
Sure, with enough discipline you can make sure that nobody uses these “private” modules, but the same could be said about private functions, and yet we have them in a language. Unfortunately, disciple and conventions fades when we face a deadline, are tired, unexperienced or new on the team. That’s why having a help from the compiler is essential. If we care about visibility of a function, why shouldn’t we care about visibility of a module? After all, the purpose of both of them is to organise code.
