Goal:
  
  G : t
  x : V.t
  s0 : VSet.t
  p : SPath s0 x x
  s' : VSet.t
  Hs : VSet.Equal (VSet.union s0 VSet.empty) s'
  H : 0 < sweight p
  ============================
   (0 < sweight p)


DEBUG:Going to execute:
let rec do_ccl :=
            try do_atom; repeat (do_intro; try do_atom); try arith_congr;
             (solve [ split; do_ccl ])
           in
           (solve [ do_atom | use_hyps; do_ccl ]) ||
             fail "Cannot solve this goal"