Goal:
  
  G : t
  s0 : VSet.t
  s' : VSet.t
  x : V.t
  y : V.t
  z : V.t
  d : DisjointAdd x s0 s'
  e : EdgeOf x y
  p : SPath s0 y z
  IHp : forall s' : VSet.t, VSet.Subset s0 s' -> SPath s' y z
  s'0 : VSet.t
  Hs : VSet.Subset s' s'0
  u : VSet.elt
  Hu : VSet.In u s0
  ============================
   (x = u \/ VSet.In u s0)


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 := idtac; intuition_solver
     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 := idtac; intuition_solver
     of type
     tacvalue
of type
tacvalue of type tacvalue