Goal:
  
  G1 : t
  G2 : t
  on_edge : forall x y : V.t, EdgeOf G1 x y -> EdgeOf G2 x y
  vsub : VSet.Subset (V G1) (V G2)
  weight_on_edge : forall (x y : V.t) (e : EdgeOf G1 x y),
                   (on_edge x y e).π1 >= e.π1
  x : V.t
  y : V.t
  H : protect_term (lsp G1 x y = None)
  ============================
   (None <= lsp G2 x y)%nbar


DEBUG:Going to execute:
<coq-core.plugins.ltac::contradiction@0> $1
Level 0: Backtrace:

No primitive equality found.