Definition unfold_reptype {t} (v: reptype t): REPTYPE t :=
  @eq_rect Type (reptype t) (fun x: Type => x) v (REPTYPE t) (reptype_eq t).Definition fold_reptype {t} (v: REPTYPE t): reptype t :=
  @eq_rect_r Type (REPTYPE t) (fun x: Type => x) v (reptype t) (reptype_eq t).

Lemma unfold_fold_reptype: forall t (v: REPTYPE t), unfold_reptype (fold_reptype v) = v.