Document and test 'let-alist' support for indexing

* etc/NEWS: Announce 'let-alist' support for indexing.
* test/lisp/emacs-lisp/let-alist-tests.el (let-alist-numbers):
Add a test for 'let-alist's support for indexing.
* doc/lispref/lists.texi (Association Lists): Document indexing
with 'let-alist'.  (Bug#66509)

1 files changed, 6 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 3dc0e0a7677..8a139cb03ca 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -2854,6 +2854,12 @@ function 'load-path-filter-cache-directory-files', calling 'load' will
 cache the directories it scans and their files, and the following
 lookups should be faster.
 
++++
+** 'let-alist' supports indexing into lists.
+The macro 'let-alist' now interprets symbols containing numbers as list
+indices.  For example, '.key.0' looks up 'key' in the alist and then
+returns its first element.
+
 ** Lexical binding
 
 ---