Static typecheckers help you catch errors early and keep your code safe. They also make debugging easier. In this course, you see how a typechecker works and how you can build one step by step.
You may ask: What is type checking? What is type inference? How do type rules work? Is my language weak or strong? And how do I build a typechecker at all? This course gives clear answers with a full hands-on build.
Many books focus on theory and treat types as abstract math. This course takes a more direct path. You build a real static typechecker for a real language in a few hours. Every idea comes with clear code and live examples.
You start coding in the first lecture. You learn how a typechecker fits into a language stack and why it helps you grow as an engineer.
What You Learn
You build a static typechecker similar to the ones used in Java, TypeScript, and other typed languages. You learn core ideas from type theory only when they help you code the next step.
Prerequisites
You do not need any formal background in type theory. But you should know how an interpreter works. The optional course Building an Interpreter from scratch helps with this.
If you understand terms like eval, closure, scope chain, and environment, you are ready to start. If not, take the interpreter course first.
Who This Course Is For
This course is for engineers who want to build complex systems and learn how static analysis works. It is also for anyone who builds a language, enjoys compilers, or wants a clear view of type systems.
Tools You Use
You do not need a special “types-first” language to build a typechecker. You use plain JavaScript to keep the ideas simple. The logic then maps cleanly to TypeScript, Rust, OCaml, Python, C++, or any other language you prefer.
How You Learn
You write each part of the typechecker yourself. The video lessons show the full source code, but the repo includes tasks marked with /* Implement here */. You fill these in during the course so you understand every detail.
