patty VS Kind2

This comment is misleading &| misinformed.

Sum types are built-in [1] for formal parameters. `nil` is only for `ref|ptr` types. In much code you can just use stack allocated value types and there is neither GC concern nor nil concern, but there is also a mode to help: https://nim-lang.github.io/Nim/manual_experimental_strictnot...

Nim has an easy-ish to use Lisp-like syntax macro system where you just receive & process an AST. So, to do the rest you can make libraries adding the feature without relying upon upstream compiler: such as https://github.com/beef331/sumtypes for variables with sum types or pattern matching libs like https://andreaferretti.github.io/patty/ | https://github.com/alehander92/gara.

...except that macros don't change the syntax of the language! They just offer convenience on top of it, most common example is the `=>` lambda operator from the `sugar` module. I do agree, that the pattern matching macro presented in the article is a bit hard to get used to, but you don't have to, if you don't like pattern matching. And of course there are plenty of alternatives available as well, the simplest one imo is https://github.com/andreaferretti/patty

Agreed. Even from a PLT perspective, I prefer Kind2 by the Kindelia Foundation for supporting inductive theorem proving (and hopefully some level of dependent types), as well as being faster to boot.

I agree. Keep in mind our language (Kind-Lang) does target the HVM, and it is really promising. The type-checker is the fastest among proof assistants, by far; the error messages are really nice; it has a fully dependent type system which is a breath of fresh air to work with. It is still not production ready though (mostly due to lack of IO), but is the extend of our effort on that direction. We hope other lang developers get encouraged to target the HVM to. Elm and Idris are great candidates for that IMO.

Another very small proof system: https://github.com/moonad/formcorejs

The core implementation is under 700 lines of JS, including the parser: https://github.com/moonad/FormCoreJS/blob/master/FormCore.js

The author has since moved on to building a runtime with optimal evaluation (https://github.com/kindelia/hvm) and a new proof language on top of that (https://github.com/Kindelia/Kind2) with considerably better performance than existing proof systems.