Module Call.FuncArg

Little abstraction over arguments: currently actual args, we'll want formal args later

type 'arg_payload t = {
  1. exp : IR.Exp.t;
  2. typ : IR.Typ.t;
  3. arg_payload : 'arg_payload;
}
val map_payload : f:('arg_payload -> 'arg_payload') -> 'arg_payload t -> 'arg_payload' t