anchor.diff:                // GM: No. We could be in a contradictory environment.
                 then let guard = if U.eq_tm t1 t2 = U.Equal
                                  then None
  -                               else Some <| mk_eq2 env t1 t2 in
  +                               else Some <| mk_eq2 orig t1 t2 in
                      solve env (solve_prob orig guard [] wl)
                 else rigid_rigid_delta env orig wl head1 head2 t1 t2
            else rigid_rigid_delta env orig wl head1 head2 t1 t2
  
positive.code:                 if (may_relate head1 || may_relate head2) && wl.smt_ok
                  then let guard =
                          if problem.relation = EQ
                          then mk_eq2 env t1 t2
                          else let has_type_guard t1 t2 =
                                  match problem.element with
                                      | Some t -> U.mk_has_type t1 t t2
  
negative.code: (* --------------------------------------------------------- *)
  (* </new_uvar>                                               *)
  (* --------------------------------------------------------- *)
  
  (* Instantiation of unification variables *)
  type uvi =
  