`tree` refered in fact out to the parameter of `typed1`. It is the same reference as the `atd: Annotated` parameter of `typedAnnotated`. The main difference is that we don't set the `tpe` field of the untyped tree `atd`. Instead we create a new `Annotated` instance and set its type. Also the new `Annotated` instance has the typed `arg1` as body - I think it's better to put that into the `original` than the un-typed `arg`