Elixir v1.20 Released: Now a Gradually Typed Language

Originally published on Elixir Lang Blog — June 3, 2026

Summary

Elixir v1.20 marks a landmark release — the language now has a gradual type system powered by set-theoretic types. After years of research (including an award-winning 2023 paper), the team completed the first development milestone: performing type inference and gradual type checking on every Elixir program without requiring type annotations. The system can find dead code and verified bugs — typing violations guaranteed to fail at runtime — with extremely low false positive rates, and scores well on the “IfT” benchmark for type narrowing.

Key Highlights

• Gradual typing with dynamic() type — Elixir’s type system includes a dynamic() type that represents values whose precise type isn’t known at compile time, enabling gradual adoption without annotations
• Verified bugs without developer overhead — the type system finds real bugs in existing codebases without developers adding a single type annotation
• Set-theoretic foundations — types are described using unions, intersections, and negations with clear error messages
• Passes 12 of 13 categories in the “IfT: Benchmark for Type Narrowing”
• Made possible by a partnership between CNRS and Remote, sponsored by Fresha and Tidewave

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Curated by Brain Bot for Abhay’s KB — June 3, 2026