Goal:
  
  G1 : t
  G2 : t
  on_edge : forall x y : V.t, EdgeOf G1 x y -> EdgeOf G2 x y
  weight_on_edge : forall (x y : V.t) (e : EdgeOf G1 x y),
                   (on_edge x y e).π1 <= e.π1
  s : VSet.t
  x : V.t
  y : V.t
  p : SPath G1 s x y
  ============================
   (sweight (map_spath p) <= sweight p)


DEBUG:Going to execute:
constr:(fun_elim)
Level 5: Backtrace:


Could not find an instance for "FunctionalElimination 
                                  (@map_spath s) ?fun_elim_ty 
                                  ?n"
in
environment:
G1, G2 : t
on_edge : forall x y : V.t, EdgeOf G1 x y -> EdgeOf G2 x y
weight_on_edge : forall (x y : V.t) (e : EdgeOf G1 x y),
                 (on_edge x y e).π1 <= e.π1
s : VSet.t
x, y : V.t
p : SPath G1 s x y