This English version is an AI translation of my original article on Qiita (in Japanese).
About this article
On June 3, 2026, Elixir 1.20 shipped with a type system. But it aims at something a little different from the type systems we are used to, the ones where you write types to buy safety.
This article started from my own questions, which I worked through with an AI agent. We went to primary sources (the official blog, the docs, the paper), and in the end I installed Elixir 1.20 and checked how the type checker actually behaves. I may still have gotten things wrong, so if you notice anything, I would be glad to hear it in the comments.
What the type system aims for: soundness
