I want to build my own version of TypeScript, mainly its type-checking component, but I don't have much background in compilers yet. I was thinking of reading the Go implementation line by line and modifying it as I learn, but the repository has many folders and files whose names aren't immediately clear. Where should I begin, and what's a good method for navigating and understanding a large codebase like this?
3 Answers
Try to find the program’s entry point and trace the main execution path from there. For a compiler or type checker, follow how source text is loaded, parsed into an abstract syntax tree, bound, and then checked. Use the repository’s README, build scripts, tests, and package documentation to figure out what each directory is responsible for instead of reading every file from top to bottom.
An AI assistant can help you navigate a large codebase if you give it focused questions. For example, ask it to explain one directory, trace a particular function, or describe how a type-checking error is produced. Verify its explanations by following the actual code and tests, since it can miss details or invent connections.
Before diving into the implementation, learn the basic compiler concepts first. Crafting Interpreters is a useful starting point because it explains parsing, syntax trees, interpretation, and related ideas in a practical way. Then look at the specific TypeScript implementation and identify how those concepts map onto its packages and types.
This works best when you already have a specific file, function, or call path in front of you. Broad questions about the entire repository tend to produce vague answers, so break the investigation into small pieces.