Term Rewrite System for TypeScript

Goals

Ability to define pattern matching

type T = { type: "num"; num: number } | { type: "str"; str: string };

const x: T = { type: "num", num: 17 };

match(x, [
  [{ type: "num", num: n }, n + n],
  [{ type: "str", str: s }, s.length],
]);

Progress

basic expressions, statements, and declarations

• (Nov 16, 2024) lexical declarations (let, const) and lexical variables
• (Nov 21, 2024) arrow functions (args) => {body} and (args) => expr
• arrow functions initializer expressions, e.g., (x = 12) => x;
• function declarations
• return statement
• if statement
• while loop
• for loop
• object literals
• array literals
• class declarations

types

• type declarations type T = ... and typed lexical declarations const x: T = ...
• arrow functions parameter types, e.g., (x: T) => body
• arrow functions type parameters, e.g., <T>(x: X) => body

rewrite forms

• (Nov 18, 2024) splice(() => {body})
• rewrite_rules(x, [pattern, literals?, template]*, expr) (aka. let-syntax with syntax-rules)

separate compilations

• script serialization
• exports
• dependency tracking for module visits and invocations

general improvements

• (Nov 23, 2024) make a proper pretty printer (using prettier for now)
• add source locations to ast/stx forms (most likely to tags).

code quality

• (Nov 19, 2024) unit testing
• code coverage reports
• remove unused exports in code base

Some references

• dsherret/ts-nameof#121