[Emacs-diffs] emacs-25 80128a7: Fix stability confusion in sort-tests

[Paul Eggert]

branch: emacs-25
commit 80128a784912096c6b0ee46b76b068e019cff057
Author: Paul Eggert <address@hidden>
Commit: Paul Eggert <address@hidden>

    Fix stability confusion in sort-tests
    
    Problem reported by Philipp Stephani (Bug#23205).
    * test/automated/sort-tests.el:
    (sort-tests--insert-words-sort-and-compare):
    Don’t assume that reversing a sorted list is the same
    as sorting with the reverse predicate.  This is not true
    for stable sorts when items compare equal.
---
 test/automated/sort-tests.el |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/test/automated/sort-tests.el b/test/automated/sort-tests.el
index 5297329..f3a182c 100644
--- a/test/automated/sort-tests.el
+++ b/test/automated/sort-tests.el
@@ -40,8 +40,10 @@
     (funcall function reverse (point-min) (point-max))
     (let ((sorted-words
            (mapconcat #'identity
-                      (let ((x (sort (copy-sequence words) less-predicate)))
-                        (if reverse (reverse x) x))
+                      (sort (copy-sequence words)
+                            (if reverse
+                                (lambda (a b) (funcall less-predicate b a))
+                              less-predicate))
                       separator)))
       (should (string= (substring (buffer-string) 0 -1) sorted-words)))))