Semi-automatic refactoring tools is just one part of what a type system enables. A much bigger benefit in my opinion is that it immediately highlights issues in

Semi-automatic refactoring tools is just one part of what a type system enables. A much bigger benefit in my opinion is that it immediately highlights issues in your code while you are refactoring. Basically answer "What do I still need to change to finish the refactoring?". Unit testing also gives you some of this, but is typically much slower - both in execution time, and the additional time it takes to figure out where the issue is.