Don't increment array index in cl-loop twice (Bug#40727)

* lisp/emacs-lisp/cl-macs.el (cl--parse-loop-clause): Put the temp-idx
increment in cl--loop-body, leaving just the side-effect free testing
of the index for both cl--loop-body and cl--loop-conditions.
* test/lisp/emacs-lisp/cl-macs-tests.el (cl-macs-loop-and-arrays):
Extend test to cover this case.

2 files changed, 5 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/cl-macs.el b/lisp/emacs-lisp/cl-macs.el
index fef8786b599..3317c580028 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -1320,8 +1320,9 @@ For more details, see Info node `(cl)Loop Facility'.
                       (temp-idx (make-symbol "--cl-idx--")))
                   (push (list temp-vec (pop cl--loop-args)) loop-for-bindings)
                   (push (list temp-idx -1) loop-for-bindings)
+                  (push `(setq ,temp-idx (1+ ,temp-idx)) cl--loop-body)
                   (cl--push-clause-loop-body
-                   `(< (setq ,temp-idx (1+ ,temp-idx)) (length ,temp-vec)))
+                   `(< ,temp-idx (length ,temp-vec)))
                   (if (eq word 'across-ref)
                       (push (list var `(aref ,temp-vec ,temp-idx))
                             cl--loop-symbol-macs)
diff --git a/test/lisp/emacs-lisp/cl-macs-tests.el b/test/lisp/emacs-lisp/cl-macs-tests.el
index 77609a42a99..983e79ac57c 100644
--- a/test/lisp/emacs-lisp/cl-macs-tests.el
+++ b/test/lisp/emacs-lisp/cl-macs-tests.el
@@ -43,6 +43,9 @@
   "Bug#40727"
   (should (equal (cl-loop for y = (- (or x 0)) and x across [1 2]
                           collect (cons x y))
+                 '((1 . 0) (2 . -1))))
+  (should (equal (cl-loop for x across [1 2] and y = (- (or x 0))
+                          collect (cons x y))
                  '((1 . 0) (2 . -1)))))
 
 (ert-deftest cl-macs-loop-destructure ()