Elixir: Type inference of all constructs and the next 15 months

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A new Elixir blog post/announcement has been posted!

Today we celebrate 15 years since Elixir’s first commit! To mark the occasion, we are glad to announce the first release candidate for Elixir v1.20, which performs type inference of all language constructs, with increasing precision.

In this blog post, we will break down exactly what this means, and what to expect in the short and medium term of the language evolution (roughly the next 15 months).

Types, in my Elixir?

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.

Our goal is to introduce a type system which is:

• sound - the types inferred and assigned by the type system align with the behaviour of the program

• gradual - Elixir’s type system includes the dynamic() type, which can be used when the type of a variable or expression is checked at runtime. In the absence of dynamic(), Elixir’s type system behaves as a static one

• developer friendly - the types are described, implemented, and composed using basic set operations: unions, intersections, and negations (hence it is a set-theoretic type system)

However, I want to emphasize what the gradual typing means in Elixir. Many gradual type systems have the any() type, which, from the point of v...

Get the full details here: Type inference of all constructs and the next 15 months - The Elixir programming language