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:
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