(************************************************************************)
(*         *   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)         *)
(************************************************************************)
(*Set Debug SsrMatching.*)
Tactic Notation "at" "[" ssrpatternarg(pat) "]" tactic(t) :=
let name := fresh in
let def_name := fresh in
ssrpattern pat;
intro name;
pose proof (refl_equal name) as def_name;
unfold name at 1 in def_name;
t def_name;
[ rewrite <- def_name | idtac.. ];
clear name def_name.

Lemma test (H : True -> True -> 3 = 7) : 28 = 3 * 4.