test/regress/regress0/let.smtv1.smt2

   1 (set-option :incremental false)
   2 (set-info :status unsat)
   3 (set-logic QF_UF)
   4 (declare-sort U 0)
   5 (declare-fun a () U)
   6 (declare-fun b () U)
   7 (declare-fun f (U) U)
   8 (check-sat-assuming ( (let ((_let_0 (= a b))) (and _let_0 (not _let_0))) ))