Goal:
  
  G : t
  invG : invariants G
  acG : acyclic_no_loop G
  x : V.t
  y : V.t
  hx : VSet.In x (V G)
  hy : VSet.In y (V G)
  nxy : Z
  hxy : (lsp G x y <= Some nxy)%nbar
  k : nat
  H : 0 <= 0
  ============================
   (k = match Z.of_nat k with
        | Z.pos p => Pos.to_nat p
        | _ => 0%nat
        end)


DEBUG:Going to execute:
match goal with
           | H:~ _ |- _ => solve [ case H; trivial ]
           end
Level 1: Backtrace:

No such assumption.
Level 0: Backtrace:

No such assumption.
Level 0: Backtrace:

No such assumption.
Level 0: Backtrace:

No such assumption.