Goal:
  
  G : t
  HG : acyclic_no_loop
  s : VSet.t
  x : V.t
  y1 : V.t
  y2 : V.t
  n : Z
  He : EdgeSet.In (y1, n, y2) (E G)
  Hy : VSet.In y1 s
  ============================
   (lsp0 s x y1 + Some n <= lsp0 s x y2)%nbar


DEBUG:Going to execute:
generalize eq_refl; pattern x at - 1
Level 1: evaluation returns
generalize eq_refl; pattern x at - 1; case x
where
x := lsp0 s x y1
of type
constr of type tacvalue