eqwalizer VS Gradualizer

I don't think the implementation itself is at fault, but yes, I do think that the design of dialyzer makes it an (at times) faulty type checker. The unfortunate reality of a type checker that fails sometimes is that it makes it mostly useless because you can never trust that it'll do the job.

To be clear, I've had it fail in a function where I've literally specced that very function to return a `binary` but I'm returning an `integer` in one of the cases. This is a very shallow context but it can still fail. Now add more functions, maybe one more `case`.

I think an entire rethink of type checking on the BEAM had to be done and that's why eqWalizer[0] was created and why Elixir is looking to add an actual sound, well-developed type checker. Gleam[1] I would assume is just a Hindley-Milner system so that's completely solid. `purerl`[2] is just PureScript for the BEAM so that's also Hindley-Milner, meaning it's solid. `purerl` has some performance issues caused by it compiling down to closures everywhere but if you can pay that cost it's actually pretty fantastic. With that said my bet for the best statically typed experience right now on the BEAM would be `gleam`.

0 - https://github.com/WhatsApp/eqwalizer

1 - https://gleam.run

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

While it's not static-typing, compile-time type checking for Erlang have come a long way: Eqwalizer works pretty well - but I may be biased since my employer sponsors the project.

1. https://github.com/WhatsApp/eqwalizer

Note there is also research happening in this area by the Elixir team. The WhatsApp is also working on static types for Erlang, which I am certain will be available for Elixir too at some point.

From the discord blog posts it seems that elixir powers the chat system, with rust and python as the other two main languages in their stack.

As for whatsapp, they are mainly a erlang shop and yesterday they open sourced a type checker for erlang:

https://github.com/WhatsApp/eqwalizer

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