Declarative Macros

Declarative macros let you define compile-time code transformations entirely in TypeScript, using pattern-matching syntax inspired by Rust’s macro_rules!. No Rust toolchain is involved — the macro lives in the same .ts file that uses it.

import { macroRules } from "macroforge/rules";

const $double = macroRules`
  ($x:Expr) => ($x) * 2
`;

const four = $double(2); // → (2) * 2

They run as a pre-pass, before attribute and derive macros, so a declarative macro can expand into code that later macros then process.

Full documentation

This page is a conceptual overview. The complete reference lives in its own section:

• Declarative Macros overview — what they are and when to use them
• Defining Macros — tag form, object form, scoping
• Patterns & Fragments — all 11 fragment specifiers
• Repetitions & Backtracking — variable-length patterns
• Expansion & Hygiene — contexts, IIFE wrapping, composition
• Type-Position Macros — $Macro<T>
• Reverse Monomorphization — shared runtime helpers
• Cross-File Macros & Diagnostics — imports and error reference