> The hardcore “sound types” crowd believes that anybody using dynamic types is doomed.

What they believe is that "dynamic types" is a misnomer, and if you think your program is checking dynamic types, it is in fact doing runtime pattern matching over a variant record. There's nothing wrong with pattern matching and variant records; but conflating them with types is just nutty, and using them pervasively as part of the ordinary flow of code is no different than programming in old-style VB.

I suppose that you mean that it should be "checking types dynamically", rather than "checking dynamic types"?

I don’t think many people programming in dynamic languages would die on that hill. Avoiding types is kind of the allure, I think?

At the expense of having to write more tests that a type system could have solved at compile time, and likely catch more runtime logic bugs as well.

For the record I am a convert. Types have made my developer life much happier, especially working with unfamiliar code across multiple projects/teams. When you treat your builds as long term proofs your confidence level increases dramatically.

I don’t disagree :)

Doomed is a bit of a strong word. I personally prefer static types because they reduce the number of unit tests I have to write, and at a higher level (following from this) they can inform the design of a system in a way that encourages robustness. Algebraic data types are not really inherent in functional programming at all; as you mention you can do it just fine in a dynamic language and a good chunk of ADTs and type stuff translates to say Rust as well.