| Flat2: flat2 → item2 (* non-binding item *)
.
+(* Basic inversion lemmas ***************************************************)
+
+fact destruct_sort_sort_aux: ∀k1,k2. Sort k1 = Sort k2 → k1 = k2.
+#k1 #k2 #H destruct //
+qed-.
+
(* Basic properties *********************************************************)
lemma eq_item0_dec: ∀I1,I2:item0. Decidable (I1 = I2).