Goal:
  
  G : t
  fuel : nat
  s : VSet.t
  x : V.t
  z : V.t
  IHfuel : forall (s : VSet.t) (x z : V.t),
           lsp00_fast fuel s x z = lsp00 fuel s x z
  ============================
   ((if VSet.mem x s
     then
      EdgeSet.fold
        (fun '(src, w, tgt) (acc : Nbar.t) =>
         if is_left (V.eq_dec src x)
         then max acc (Some w + lsp00_fast fuel (VSet.remove x s) tgt z)
         else acc) (E G) (if is_left (V.eq_dec x z) then Some 0 else None)
     else if is_left (V.eq_dec x z) then Some 0 else None) =
    (if VSet.mem x s
     then
      fold_left max
        (map
           (fun '(n, y) => (Some n + lsp00 fuel (VSet.remove x s) y z)%nbar)
           (succs x)) (if is_left (V.eq_dec x z) then Some 0 else None)
     else if is_left (V.eq_dec x z) then Some 0 else None))


DEBUG:Going to execute:
<coq-core.plugins.ssreflect::ssrtclintros@0> arg