Function field_name_from_place 

pub(crate) fn field_name_from_place<'tcx>(
    tcx: TyCtxt<'tcx>,
    adt_def_id: DefId,
    place: &ContractPlace<'tcx>,
) -> Option<String>

The field name selected by the first Field projection of place on adt_def_id (e.g. ptr in self.ptr), if any.