the one reason I like single expression and inferred return type is refactoring, especially during the prototyping/tdd phase. much faster than having to change return type because I now decide I want a nullable, then not-nullable, then a completely different type. at that point I have tests however, so the issue with inferred lambda and thus code that is not run does not exist.

You're right @thanksforallthefish. If we have tests then our codebase will always have a safe-guard.