Minimal reproducible test for this error message: /usr/lib/haxe/std/sys/db/Object.hx:29: characters 2-11 : You cannot use @:build inside a macro : make sure that your enum is not used in macro

BuildInMacroTests.hx

import haxe.macro.Expr;
import haxe.macro.Context;
import neko.Lib;

class BuildInMacroTests {
    public static function main() {
        var s:MyModel = new MyModel();
        Formatter.__Output_Formatter( s );
    }
}

class MyModel extends sys.db.Object 
{
    var id:Int;
    var name:String;
}

private class Formatter {

    public static macro function __Output_Formatter(output : Expr) : Expr {
        return output;
    }
}

Moving "Formatter" do a different .hx file / module solves the issue.

You can also wrap "MyModel" and "BuildInMacroTests" in #if !macro ... #end conditionals which also resolves the issue.