usage: "haxe Main.hxml". -D dumpの効果により、dump/にマクロ展開後のASTが出力されます

Main.hx

@:build(MyMacro.build()) class Main {
	public static function main() {
		trace(hello());
	}
}

Main.hxml

-main Main
-D dump
-js Main.js
-cmd node Main.js

MyMacro.hx

import haxe.macro.Expr;
class MyMacro {
	macro public static function build() : Array<Field> {        
		var pos = haxe.macro.Context.currentPos();
		var fields = haxe.macro.Context.getBuildFields();

		/*
		static function hello(): String { return "Hello, world!"; }
		というフィールドを生成する
		*/

		var tstring = TPath({ pack : [], name : "String", params : [], sub : null });
		var e1 = {expr: EConst(CString("Hello, world!")), pos: pos};
		var e2 = {expr: EReturn(e1), pos: pos};
		var ftype = FFun({args:[], expr: e2, ret: tstring});
		fields.push({ name : "hello", pos: pos, kind: ftype, access: [AStatic]});
		return fields;
	}
}