(* The derivation that is plugged in is usually canonical, i.e., [m] is zero, but we do not require this. *)
(* In the worst case, the height of the new derivation is the sum of the heights of the original derivations, due to the way the derivations are plugged in at variables. *)

Lemma inversion_JTyAbs:
forall E t T,
j 0 E (TAbs t) (TyForall T) ->
j 0 (map (shift 0) E) (TAbs t) T.