Hi, I'm struggling to get this little piece of code running in JS:

@Js class Main : Test {
    Void testItBlock() {
        fn := Field.makeSetFunc([User#name:"Dude"])
        user := User(fn)
        echo(user->name)
    }
}

@Js class User {
    Str? name
    new make(|This| f) { f(this) }
}

When run with fant in the JVM all is okay, but when in NodeJS via testRunner I get the following error:

TypeError: Cannot read property 'size' of undefined
    at fan.sys.Type.doReflect 
    at fan.sys.Type.reflect 
    at fan.sys.Type.$mergeType 
    at fan.sys.Type.doReflect 
    at fan.sys.Type.reflect 
    at fan.sys.Type.slot 
    at fan.acme.Main.testItBlock 
    at testRunner 

This looks like the same issue as 2770