Goal:
  
  G : t
  a : sigma
        (fun index : sigma (fun _ : VSet.t => sigma (fun _ : V.t => V.t)) =>
         SPath (pr1 index) (pr1 (pr2 index)) (pr2 (pr2 index)))
  b : sigma
        (fun index : sigma (fun _ : VSet.t => sigma (fun _ : V.t => V.t)) =>
         SPath (pr1 index) (pr1 (pr2 index)) (pr2 (pr2 index)))
  H : NoConfusion_SPath a b
  ============================
   (a = b)


DEBUG:Going to execute:
intros;
            match goal with
            | |- ?R ?a ?b =>
                  CoreTactics.destruct_sigma a; CoreTactics.destruct_sigma b;
                   destruct a; DepElim.depelim b; 
                   simpl in * |-;
                   CoreTactics.on_last_hyp
                    ltac:(fun id =>
                            hnf in id;
                             CoreTactics.destruct_tele_eq id || destruct id);
                   (solve [ constructor ])
            | |- ?f ?a ?b _ = _ => solve_noconf_inv_eq a b
            end