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.

2 files changed, 7 insertions, 2 deletions

diff --git a/lisp/emacs-lisp/seq.el b/lisp/emacs-lisp/seq.el
index 20610a7027d..e5004f8cdab 100644
--- a/lisp/emacs-lisp/seq.el
+++ b/lisp/emacs-lisp/seq.el
@@ -4,7 +4,7 @@
 
 ;; Author: Nicolas Petton <nicolas@petton.fr>
 ;; Keywords: sequences
-;; Version: 2.17
+;; Version: 2.18
 ;; Package: seq
 
 ;; Maintainer: emacs-devel@gnu.org
@@ -349,7 +349,8 @@ found or not."
   "Return the first element in SEQUENCE that is equal to ELT.
 Equality is defined by TESTFN if non-nil or by `equal' if nil."
   (seq-some (lambda (e)
-              (funcall (or testfn #'equal) elt e))
+              (when (funcall (or testfn #'equal) elt e)
+                e))
             sequence))
 
 (cl-defgeneric seq-position (sequence elt &optional testfn)
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))