Edebug doesn't deal well with backtracking out of definitions, see
Bug#41988. Rather than trying to support this rare situation (e.g. by
implementing a multipass parser), prevent it by adding an implicit
gate.
* lisp/emacs-lisp/edebug.el (edebug--match-&-spec-op): Disable
backtracking when hitting a &define keyword.
* test/lisp/emacs-lisp/edebug-tests.el
(edebug-tests-duplicate-&define): New unit test.
(edebug-tests--duplicate-&define): New helper macro.
* doc/lispref/edebug.texi (Backtracking): Mention &define in the list
of constructs that disable backtracking.
* etc/NEWS: Document new behavior.
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with Emacs. This includes some text files of documentation for GNU
Emacs or of interest to Emacs users, and the file of dumped docstrings
for Emacs functions and variables.
COPYRIGHT AND LICENSE INFORMATION FOR IMAGE FILES
File: emacs.icon
Author: Sun Microsystems, Inc
Copyright (C) 1999, 2001-2021 Free Software Foundation, Inc.
License: GNU General Public License version 3 or later (see COPYING)
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