* Add check in MethodType construction that required, optional, and   varargs are in the right order. * Progress on to_contract, code to check arguments (accounting for   optional and varargs).
* Add check in MethodType construction that required, optional, and
  varargs are in the right order.
* Progress on to_contract, code to check arguments (accounting for
  optional and varargs).

plum-umd/rdl