New macro seq-let, providing destructuring support to seq.el

* lisp/emacs-lisp/seq.el (seq-let): New macro.  `seq-let' is similar
to `cl-destructuring-bind' but works on all sequence types supported
by `seq.el'.  Bump version number to 1.6.
* test/automated/seq-tests.el: Add tests for seq-let.
* doc/lispref/sequences.texi: Add documentation for seq-let.

1 files changed, 17 insertions, 0 deletions

diff --git a/test/automated/seq-tests.el b/test/automated/seq-tests.el
index 7f6e06cc4b6..e1e8ae002d0 100644
--- a/test/automated/seq-tests.el
+++ b/test/automated/seq-tests.el
@@ -276,5 +276,22 @@ Evaluate BODY for each created sequence.
         (v2 [2 4 6]))
     (should (seq-empty-p (seq-difference v1 v2)))))
 
+(ert-deftest test-seq-let ()
+  (with-test-sequences (seq '(1 2 3 4))
+    (seq-let (a b c d e) seq
+      (should (= a 1))
+      (should (= b 2))
+      (should (= c 3))
+      (should (= d 4))
+      (should (null e))))
+  (let ((seq '(1 (2 (3 (4))))))
+    (seq-let (_ (_ (_ (a)))) seq
+      (should (= a 4))))
+  (let (seq)
+    (seq-let (a b c) seq
+      (should (null a))
+      (should (null b))
+      (should (null c)))))
+
 (provide 'seq-tests)
 ;;; seq-tests.el ends here