Ty is a fast Python type checker and language server. Ty is built with Rust, and there are a lot of interesting technical challenges involved in making it a useful tool.

Building a Python type checker is a hard task; however, the design of Ty provides a joyful developer experience for contributors. In this talk, we will look at how the Ty codebase is structured to make development simple, and what design choices make it pleasant to work on.

We will cover: - How Ty goes from a Python program to a diagnostic, and what parts are most important if you want to contribute. - Data layout and ownership model of structs in Rust. - Salsa solves challenge of incremental type checking across many files. - Tooling for tests, snapshot testing during development and type checking open source projects in CI.