[vasilakisfil]

You are bringing in Rust's amazing type system but that assumes that you understand how the 3rd party system behaves. Otherwise your types will be very loose (i.e. String ? could be anything in there) not gaining anything compared to Javascript/Ruby/Python.

If I know how the external system will behave then yes Rust is better, obviously. However I was talking on the case of figuring out, as the article says. Sometimes you are not even there, you integrate with an external (legacy? undocumented? buggy?) system and you need to understand what's going on. In these cases a dynamic language is so much more productive than Rust and any Rust-like language.