This sounds like a bad interview IMO. But also, don’t be this interviewee. Solving a problem like this with the type system is setting off all kinds of “too cl

This sounds like a bad interview IMO. But also, don’t be this interviewee. Solving a problem like this with the type system is setting off all kinds of “too clever for their own good” alarm bells. The goal of a coding interview is to showcase as concisely as possible that you know the craft of software engineering. Fizzbuzz should not be considered an IQ test. The progressive requirements in the interview, while clunky, are getting at the reality of software development: there rarely exists a spec for what you are building. You need to be flexible to future requirements, and you need to write maintainable code that others on your team can understand.