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(*         *   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)           *)
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(*    //   *    This file is distributed under the terms of the         *)
(*         *     GNU Lesser General Public License Version 2.1          *)
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(* (c) Copyright 2006-2016 Microsoft Corporation and Inria.                  *)
wlog _ : b / b = true.
case: b; [ by apply | by rewrite orbC ].
wlog suff: b /  b || ~~b.
by case: b.
by case: b.
Qed.

Lemma test2 b c (H : c = b) : b || ~~b.