Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  n : Z
  x : V.t
  y : V.t
  n0 : (Some n <= lsp G x y)%nbar -> False
  H : is_true false
  ============================
   (Some n <= lsp G x y)%nbar


DEBUG:Going to execute:
match goal with
           | |- _ -> _ => intro; t_tauto_intuit
           | |- _ => t_reduce; t_solver
           end