Module AddCommExt_Transparent <: ADD_COMM_EXT.
End AddCommExt_Transparent.
Print Assumptions AddCommExt_Opaque.add_comm_ext.
(* Should answer: extensionality *)
Print Assumptions AddCommExt_Transparent.add_comm_ext.
(* Should answer: extensionality *)

Lemma add1_comm_ext_opaque :
(fun x => x + 1) = (fun x => 1 + x).