+and term = TSort of attrs * int (* attrs, hierarchy index *)
+ | TLRef of attrs * int * int (* attrs, position indexes *)
+ | TGRef of attrs * uri (* attrs, reference *)
+ | TCast of attrs * term * term (* attrs, domain, element *)
+ | TAppl of attrs * term list * term (* attrs, arguments, function *)
+ | TProj of attrs * lenv * term (* attrs, closure, member *)
+ | TBind of attrs * bind * term (* attrs, binder, scope *)