* lisp/emacs-lisp/macroexp.el (macroexp--fgrep): Break cycles

* test/lisp/emacs-lisp/macroexp-tests.el: New file.

test/lisp/emacs-lisp/macroexp-tests.el

@@ -0,0 +1,36 @@
+;;; macroexp-tests.el --- Tests for macroexp.el      -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2021  Stefan Monnier
+
+;; Author: Stefan Monnier <monnier@iro.umontreal.ca>
+;; Keywords:
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;
+
+;;; Code:
+
+(ert-deftest macroexp--tests-fgrep ()
+  (should (equal (macroexp--fgrep '((x) (y)) '([x] z ((u))))
+                 '((x))))
+  (should (equal (macroexp--fgrep '((x) (y)) '#2=([y] ((y #2#))))
+                 '((y))))
+  (should (equal (macroexp--fgrep '((x) (y)) '#2=([r] ((a x)) a b c d . #2#))
+                 '((x)))))
+
+(provide 'macroexp-tests)
+;;; macroexp-tests.el ends here