Goal:
  
  G : t
  idx0 : VSet.t
  idx : sigma (fun _ : V.t => V.t)
  a : SPath (pr1 {| pr1 := idx0; pr2 := idx |})
        (pr1 (pr2 {| pr1 := idx0; pr2 := idx |}))
        (pr2 (pr2 {| pr1 := idx0; pr2 := idx |}))
  b : sigma
        (fun index : sigma (fun _ : VSet.t => sigma (fun _ : V.t => V.t)) =>
         SPath (pr1 index) (pr1 (pr2 index)) (pr2 (pr2 index)))
  e : NoConfusion_SPath {| pr1 := {| pr1 := idx0; pr2 := idx |}; pr2 := a |}
        b
  ============================
   (noConfusion_SPath_obligation_2
      {| pr1 := {| pr1 := idx0; pr2 := idx |}; pr2 := a |} b
      (noConfusion_SPath_obligation_1
         {| pr1 := {| pr1 := idx0; pr2 := idx |}; pr2 := a |} b e) = e)


DEBUG:Going to execute:
CoreTactics.destruct_sigma idx
Level 5: evaluation returns
idtac of type tacvalue