A miniature model of the Typescript compiler, intended to teach the structure of the real Typescript compiler
I started this project as part of reading Modern Compiler Implementation in ML because I wanted to learn more about compiler backends. When I started building the example compiler I found I disagreed with the implementation of nearly everything in the frontend. So I wrote my own, and found that I had just written a small Typescript.
I realised a small Typescript would be useful to others who want to learn how the Typescript compiler works. So I rewrote it in Typescript and added some exercises to let you practise with it. The resulting compiler covers a tiny slice of Typescript: just var declarations, assignments and numeric literals. The only two types are string and number.
- This is an example of the way that Typescript's compiler does things. A compiler textbook will help you learn compilers. This project will help you learn Typescript's code.
- This is only a tiny slice of the language, also unlike a textbook. Often I only put it one instance of a thing, like nodes that introduce a scope, to keep the code size small.
- There is no laziness, caching or node reuse, so the checker and transformer code do not teach you those aspects of the design.
- There's no surrounding infrastructure, like a language service or a program builder. This is just a model of tsc.
- Add EmptyStatement.
- Make semicolon a statement ender, not statement separator.
- Hint: You'll need a predicate to peek at the next token and decide if it's the start of an element.
- Bonus: Switch from semicolon to newline as statement ender.
- Add string literals.
- Add let.
- Then add use-before-declaration errors in the checker.
- Allow var to have multiple declarations.
- You'll need to convert a Symbol's declaration into a list.
- Check that all declarations have the same type.
- Add type aliases.
- You'll need to convert a Symbol's declaration into a list.
- Name resolution will need to search a symbol's declarations to see whether it has a type declaration.
- Add an ES5 transformer that converts let -> var.
- Add function declarations and function calls.
- Add arrow functions with an appropriate transform in ES5.