I agree that the problem is one of quicker feedback - the dev cycle should involve a program checking the yaml correctness (using types or otherwise) straight a

I agree that the problem is one of quicker feedback - the dev cycle should involve a program checking the yaml correctness (using types or otherwise) straight away and giving a useful error message. Too often I've seen incorrect yaml checked into git that fails with a cryptic error when deploying the application. The strength of types, in my opinion, is composability. Most config files I've seen have ultimately pulled in input from another source and used that to create their output. Types would allow the configuration to be checked for correctness even in the face of unknowns.