Fix seq-contains

Make sure seq-contains return the element of the sequence instead of t.

* lisp/emacs-lisp/seq.el (seq-contains): Fix the function.
* test/lisp/emacs-lisp/seq-tests.el: Add a regression test.

1 files changed, 4 insertions, 0 deletions

diff --git a/test/lisp/emacs-lisp/seq-tests.el b/test/lisp/emacs-lisp/seq-tests.el
index b227de36e97..c2065c6718f 100644
--- a/test/lisp/emacs-lisp/seq-tests.el
+++ b/test/lisp/emacs-lisp/seq-tests.el
@@ -181,6 +181,10 @@ Evaluate BODY for each created sequence.
     (should-not (seq-contains seq 3))
     (should-not (seq-contains seq nil))))
 
+(ert-deftest test-seq-contains-should-return-the-elt ()
+  (with-test-sequences (seq '(3 4 5 6))
+    (should (= 5 (seq-contains seq 5)))))
+
 (ert-deftest test-seq-every-p ()
   (with-test-sequences (seq '(43 54 22 1))
     (should (seq-every-p (lambda (elt) t) seq))