(************************************************************************)
(*         *   The Coq Proof Assistant / The Coq Development Team       *)
(*  v      *   INRIA, CNRS and contributors - Copyright 1999-2018       *)
(* <O___,, *       (see CREDITS file for the list of authors)           *)
(*   \VV/  **************************************************************)
(*    //   *    This file is distributed under the terms of the         *)
(*         *     GNU Lesser General Public License Version 2.1          *)
(*         *     (see LICENSE file for the text of the license)         *)
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Inductive T : Set :=
| A : T
| B : T -> T.
decide equality.
Qed.
decide equality.
Qed.
decide equality.
Qed.
decide equality.
Qed.
intros x y.
decide equality.
Qed.

Lemma lem4 : forall x y : T, {x = y} + {x <> y}.