Iain Diamond blogscot

How to Write Hygienic Rust Macros

Macro hygiene is the concept of macros that work in all contexts; they don't affect and aren't affected by anything around them. Ideally all macros would be fully hygienic, but there are lots of pitfalls and traps that make it all too easy to accidentally write unhygienic macros. This guide attempts to provide a comprehensive resource for writing the most hygienic macros.

Understanding the Module System

First, a little aside on the details of Rust's module system, and specifically paths; it is

PLEASE DON'T USE THIS GUIDE

It's over 9 years old (as of 2024-02-18), there are many better guides! You might like https://rust-unofficial.github.io/too-many-lists/

% Let's build a binary tree!

Let's build a binary tree of strings in Rust. To recap, each node in a binary tree:

must have a value

	...
	func faviconHandler(w http.ResponseWriter, r *http.Request) {
	http.ServeFile(w, r, "relative/path/to/favicon.ico")
	}
	...
	func main() {
	http.HandleFunc("/favicon.ico", faviconHandler)
	}