Add missing type to union
% What did I mean by this?
-record(type_var, {type :: type_var_reference() | id()}).
--type type() :: #type_const{} | #type_tuple{} | #type_func{} | #type_var{}.
+-type type() :: #type_const{} | #type_tuple{} | #type_func{} | #type_var{} | #type_app{}.
%
% Type variables
