Goal:
    x : V.t  y : V.t  p : VSet.t  H : x <> y  a : V.t  H1 : y = a \/ y <> a
  ============================
   ((x = a \/ VSet.In a p /\ y <> a -> (x = a \/ VSet.In a p) /\ y <> a) /\
    ((x = a \/ VSet.In a p) /\ y <> a -> x = a \/ VSet.In a p /\ y <> a))


DEBUG:Going to execute:
f x
Level 3: evaluation returns
<coq-core.plugins.tauto::with_uniform_flags@0>
where
f := fun flags => <Coq.Init.Tauto.intuition_gen> flags tac
     where
     tac := progress VSetDecide.MSetDecideAuxiliary.substMSet; intuition
             VSetDecide.MSetDecideAuxiliary.fsetdec_rec
     of type
     tacvalue
of type
tacvalue of type tacvalue

Level 2: evaluation returns
<coq-core.plugins.tauto::with_uniform_flags@0>
where
f := fun flags => <Coq.Init.Tauto.intuition_gen> flags tac
     where
     tac := progress VSetDecide.MSetDecideAuxiliary.substMSet; intuition
             VSetDecide.MSetDecideAuxiliary.fsetdec_rec
     of type
     tacvalue
of type
tacvalue of type tacvalue