@macroforge/mcp-server/docs/concepts/declarative-macros.md

MCP server for Macroforge documentation and code analysis

# Declarative Macros

Declarative macros let you define build-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.

```typescript
import { macroRules } from '@macroforge/core/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](/docs/declarative-macros)** — what they are and when to use them
- **[Defining Macros](/docs/declarative-macros/defining)** — tag form, object form, scoping
- **[Patterns & Fragments](/docs/declarative-macros/patterns)** — all 11 fragment specifiers
- **[Repetitions & Backtracking](/docs/declarative-macros/repetitions)** — variable-length patterns
- **[Expansion & Hygiene](/docs/declarative-macros/expansion)** — contexts, IIFE wrapping,
  composition
- **[Type-Position Macros](/docs/declarative-macros/type-macros)** — `$Macro<T>`
- **[Reverse Monomorphization](/docs/declarative-macros/sharing)** — shared runtime helpers
- **[Cross-File Macros & Diagnostics](/docs/declarative-macros/cross-file)** — imports and error
  reference