test/regress/regress0/parallel-let.smt2

   1 (set-logic QF_UF)
   2 (set-info :status unsat)
   3 (declare-sort U 0)
   4 (declare-fun x () U)
   5 (declare-fun y () U)
   6 (assert (distinct x y))
   7 (assert (let ((x y) (y x)) (= x y)))
   8 (check-sat)
   9 (exit)