In 2022, we announced the effort to add set-theoretic types to Elixir. In June 2023, we published an award winning paper on Elixir’s type system design and said our work was transitioning from research to development. With Elixir v1.20, we have completed our first development milestone which is to perform type inference and gradually type check every Elixir program, without introducing type annotations. This means Elixir increasingly reports dead code and verified bugs: typing violations that ar...