Goal:
  
  G : t
  z : V.t
  x : V.t
  y : V.t
  z0 : V.t
  p : PathOf G y z0
  e : EdgeOf G z0 z
  i : V.t
  H : VSet.In z0 (nodes G (PathOf_add_end p e))
  source_vertex0 : VSet.In (s G) (V G)
  ============================
   (x = z0 \/ VSet.In z0 (nodes G p))


DEBUG:Going to execute:
<Coq.Init.Tauto.is_conj> flags X1; Ltac.split
Level 5: evaluation returns
<coq-core.plugins.tauto::find_cut@0>
where
k := fun id0 id1 X2 => assert X2; [ exact (id0 id1) | clear id0 ]
     where
     flags := 
     of type
     tauto_flags
of type
tacvalue of type tacvalue

Level 5: Backtrace:

Tactic failure: No matching clause.
Level 5: Backtrace:

Tactic failure: No matching clause.
Level 5: Backtrace:

Tactic failure: No matching clause.
Level 4: Backtrace:

Tactic failure: No matching clause.