writeln!(w, "\t{} {{", trait_name).unwrap();
writeln!(w, "\t\tthis_arg: orig.this_arg,").unwrap();
for (field, clone_fn, _) in generated_fields.iter() {
writeln!(w, "\t{} {{", trait_name).unwrap();
writeln!(w, "\t\tthis_arg: orig.this_arg,").unwrap();
for (field, clone_fn, _) in generated_fields.iter() {