purerl VS Gradualizer

I will put in a good word for PureScript for the beam with `purerl`. It's my go-to for writing BEAM code nowadays. Notably PureScript tooling including LSP, package management, etc., just works, so you are able to just get to work in internalizing the way OTP and other Erlangy things are expressed in a statically typed, pure language.

https://github.com/purerl/purerl & https://purerl-cookbook.readthedocs.io/ for more information. Join the PureScript discord and the #purerl channel if you want help.

purerl is a compiler for turning PureScript code into Erlang code, so that you're able to write BEAM (the Erlang virtual machine) applications using it.

You've been able to write PureScript that compiles to Erlang and has perfect interop for years, via `purerl`[0]. Using it with Elixir is as simple as adding `purerlex` as a compiler and having your PureScript code automatically compile when `mix` compiles things, and off you go.

In terms of the typing itself, it's exactly what you get in all of PureScript, strict static typing with no `any` or the like. Using `Pinto`, the de facto OTP layer in PureScript your processes are typed, i.e. their `info` messages & state are typed, which means that they are all much more like strongly typed state machines than anything else.

You can see an example of a basic `gen_server` here:

https://pastebin.com/UTEfz7Wg

The differences aren't very big in terms of what you'd expect to be doing. One small thing to note is that the `GenServer.call` expects a closure to be passed instead of having the split between `gen_server:call` & `handle_call`, removing the need for synchronizing two places for your messages being sent and handled.

0 - https://github.com/purerl/purerl

Gradualizer is a typechecker for Erlang. It's a bidirectional typechecker, which means it uses non-local type inference, i.e. a blend of typechecking with type inference. It aims to follow the principles of gradual typing, so that it's possible to add type annotations only to parts of your code, instead of the entire code base, and it's going to work with that. One of the eqwalizer authors, Ilya Klyuchnikov, contributed to Gradualizer in the past.

If you're looking for compile-time (or actually check-time) feedback you might be interested in Gradient, a gradual type checker for Elixir and a frontend to Gradualizer. These tools, while experimental, allow for applying "making illegal states unrepresentable" principle thanks to exhaustiveness checking. In general, they are more akin to the ML-style type checking than Dialyzer is.

I'm hoping that https://github.com/josefs/Gradualizer and its Elixir counterpart get us closer to what "I" want. I find dialyzer often inscrutable compared to something like OCaml's or Haskell's type errors.

I do still use it and typespecs, because it's better than no checking.

There's Gradualyzer with support for Gradual Typing on the way.

There's an effort currently being led by Facebook to create gradual type system for Erlang call Gradualizer, which should also make its way over to Elixir.

https://github.com/josefs/Gradualizer