Thanks for the feedback! We’re trying to make Gradient as user-friendly as possible - there is significant effort put into making sure it integrates nicely with Elixir, but indeed, the software is still experimental.

Could you create a ticket with an error that you consider hard to read? Or given an example here? I’ll be happy to take it forward.

That’s the never ending story of type checkers / static analysis - how to make the checker detect real problems in code on one hand, yet still be flexible enough to allow for all quirks of the language and full expressiveness on the other. However, even more so in this case, we would be extremely happy if you could report false positives on the project’s GitHub page.

Any feedback is good feedback, so keep it coming I strongly believe it might only lead to making the tool better!

Getting back to main differences.

Gradualizer has a different approach than Dialyzer in reporting errors. Dialyzer advertises that “it’s never wrong”, which is true, but sometimes its feedback is a bit hard to use (the lovely “function … has no local return” and no direct hint on what to do with it). It’s also quite slow, though it’s not as much of a problem as it used to be a few years ago.

Gradualizer reports more kinds of errors and allows for some tricks known from other statically typed functional programming languages like exhaustiveness checking - see example screenshots of Gradualizer being used with the Erlang Language Server in this post. It’s also significantly faster, as it doesn’t require generating PLTs. Actually, thanks to its speed it’s very convenient as a background tool in the editor. However, in this experimental phase, it means some false positives might get reported.

To get a better feel of what’s possible with Gradualizer, that’s not possible with Dialyzer, you might want to watch my lightning talk about typechecking Elixir from ElixirConf EU 2021 or read about the typestate pattern in Erlang.

In the long run Gradient should offer everything Gradualizer does and maybe even a bit more thanks to some macro magic

Dialyzer was build on the idea of success typing. This makes so that dialyzer can work even without user input, just based on code itself. It also tries to not report false positives quite heavily. But it comes with the downside of not detecting many of the error cases other static typing systems can detect. (The link below even argues that dialyzer is not a type system)

Gradualizer is a completely different approach. Afaik it doesn’t do type inference, so unless you manually provide typespecs it does nothing. But for the places you do provide them, it’ll statically check for errors even beyond what dialyzer would be able to detect or would acknowledge. The other big part between the lines is that you can gradually add type safety to your systems. It’ll work with as much typespecs as the code does provide.

For more details see this one:
https://github.com/josefs/Gradualizer/blob/master/talks/talk.md#comparison-with-dialyzer

Essentially both tools try to detect errors, but do that in quite different ways with therefore quite different tradeoffs.

The most recent commit to Gradualixir was almost two years ago. Can someone give me an idea of its current status and prospects? Is anyone using it as a production tool?

-r