Function classify_method_args 

pub fn classify_method_args(
    method: &Method,
    own_type_name: &str,
    wrappers: &BTreeMap<String, CWrapper>,
    closure_handlers: &[CHandler],
) -> ClassifiedMethodArgs

Classify every argument of method once. owned_retained mirrors the owned-setter rule: &self method, int return, exactly one retained handler, no &mut primitives.