Short answer is "all of it"[1]. 'match' statements in rust also exhaustive. I believe ADTs are used and checked exactly the same way as in ocaml (I've used SML

Short answer is "all of it"[1]. 'match' statements in rust also exhaustive. I believe ADTs are used and checked exactly the same way as in ocaml (I've used SML and Haskell and they are the same as there). [1] not to say dynamic failure is totally gone from the language -- but it is if you avoid both writing 'fail' and using library functions that can fail. A common example is option::get(Option<T>) -> T, which fails if the optional value is None -- it leaves a sour taste in my mouth whenever I use it, but I still do sometimes.