Goal:
    G : t  x : V.t  i : V.t  source_vertex0 : VSet.In (s G) (V G)  H0 : False
  ============================
   (False \/ i = x)


DEBUG:Going to execute:
elim H
Level 4: evaluation returns
<coq-core.plugins.tauto::is_empty@0>
where
tauto_flags := 
of type
tauto_flags
X1 := False
of type
constr of type tacvalue