Avoid duplicated character classes in rx

For example, (any digit digit) should produce "[[:digit:]]",
not "[[:digit:][:digit:]]".

* lisp/emacs-lisp/rx.el (rx--translate-any): Deduplicate character classes.
* test/lisp/emacs-lisp/rx-tests.el (rx-any): Add test case.

1 files changed, 3 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/rx.el b/lisp/emacs-lisp/rx.el
index 52a35ffa2a7..6fde27831a0 100644
--- a/lisp/emacs-lisp/rx.el
+++ b/lisp/emacs-lisp/rx.el
@@ -376,7 +376,9 @@ If NEGATED, negate the sense."
              (push (cons arg arg) conses))
             ((and (symbolp arg)
                   (let ((class (cdr (assq arg rx--char-classes))))
-                    (and class (push class classes)))))
+                    (and class
+                         (or (memq class classes)
+                             (push class classes))))))
             (t (error "Invalid rx `any' argument: %s" arg))))
     (let ((items
            ;; Translate strings and conses into nonoverlapping intervals,