The Easiest Way to Build a Type Checker
14 days ago
- #bidirectional-typing
- #type-checking
- #programming-languages
- Bidirectional Type Checking is a conceptually simple approach to type checking that demystifies the process.
- The two main directions in bidirectional type checking are inferring types and checking types, requiring some type annotations typically at function definitions.
- A simple language implementation is provided, showcasing how to infer and check types for various expressions like numbers, strings, function calls, and blocks.
- The implementation uses an abstract syntax tree (AST) to represent code, making it easier to traverse and check types.
- Context is managed using a Map to keep track of variable types, allowing for local scopes within functions or blocks.
- The article demonstrates how to extend the type checker with new features, such as addition, by adding new cases to the infer and check functions.
- The simplicity of the approach allows for easy extension to more complex features, making it a good starting point for understanding type systems.