Before Elixir typechecker gets its function type annotations syntax, the main reason to still use Dialyzer is to be able to document interfaces with argument and return types, and have these contracts (at least partially) checked by Dialyzer

I use type specs in my personal projects and at work, but only as an additional piece of documentation.

Dialyzer is not present to validate this. In my experience it has never provided much value (never found a bug that was actually causing trouble) and requires a lot of handholding.

I hope that once the native Elixir type annotation syntax is released, it will be reasonably easy to convert from the current typespecs with some LLM assitance.

We use it, but I’ve wrapped incremental dialyzer from OPT26 into a new library assay | Hex that is much faster in CI. It also has slightly more readable errors/diffs. It may go away as Elixir’s own type checking improves, but there are still a lot of places where dialyzer uncovers real issues.