A lot of things are neat because of this. Refactoring becomes trivial and safe. If you do not change the type of the refactored function, you can safely do a batch replace and everywhere the old function was used, the new one will be used after that. If you do change the type, the compiler interface will guide you through an interactive flow where you have to handle the change everywhere the function was being used. You can stop in the middle and continue later... and once you're done you just commit and push... all the while the code continues to work. Even cooler, perhaps: no unit test is re-run if not affected. And given the compiler knows the full AST of everything , it knows exactly when a test must run again.

I tried it out. Fascinating language and a completely different paradigm. The language itself is familiar, but the structure of the program is different - no files – all functions are in a database and their history. I found the language a bit difficult to navigate, but that is probably because of my experience of work with files, and having tools based on files.