Goal:
    G1 : t  ext : EdgeSet.t  x : VSet.elt
  ============================
   ((exists e : EdgeSet.elt,
       False /\ (x = e..s \/ x = e..t) /\ VSet.In x (V G1)) ->
    VSet.In x VSet.empty)


DEBUG:Going to execute:
<coq-core.plugins.ssreflect::ssrmove@1> $1 $2
DEBUG LTAC Evaluated term: VSet.empty_spec
DEBUG LTAC Evaluated term: (VSet.empty_spec _view_subject_)