While both Elixir and TypeScript are structural, they are different type systems. A set-theoretic type system is not one that has unions, intersections, negations, but rather one where the foundation of the type system is represented on top of unions, intersections, and negations. Even relations such as subtyping, compatibility, etc. are expressed as set-theoretic. We also have a very different approach to dynamic/gradual typing (which is sound): https://elixir-lang.org/blog/2023/09/20/strong-arrows-gradua...

I recommend reading Giuseppe Castagna's work for those who want to dig deeper: https://www.irif.fr/~gc/