+val errcode_of_ret : Generator_types.ret -> Generator_types.errcode
+(** Map [ret] type to the error indication that the action returns,
+ eg. [errcode_of_ret RErr] => [`ErrorIsMinusOne] (meaning that
+ these actions return [-1]).
+
+ Note that [RConstOptString] cannot return an error indication, and
+ this returns [`CannotReturnError]. Callers must deal with it. *)
+
+val string_of_errcode : [`ErrorIsMinusOne|`ErrorIsNULL] -> string
+(** Return errcode as a string. Untyped for [`CannotReturnError]. *)
+