bug#39428: 28.0.50; cl--push-clause-loop-body: eval macro arg just once

[Tino Calancha]

X-Debbugs-Cc: Stefan Monnier <monnier@iro.umontreal.ca>,dick.r.chiang@gmail.com

I think this little tweak has sense.  WDYT?


--8<-----------------------------cut here---------------start------------->8---
commit eb88afb89a8cfb760d89569e74c8ece1d1c446cb
Author: Tino Calancha <tino.calancha@gmail.com>
Date:   Tue Feb 4 21:52:06 2020 +0100

    Eval macro arg just once
    
    * lisp/emacs-lisp/cl-macs.el (cl--push-clause-loop-body):
    Use `macroexp-let2'.

diff --git a/lisp/emacs-lisp/cl-macs.el b/lisp/emacs-lisp/cl-macs.el
index 9d0fd15bc3..4c2f58907d 100644
--- a/lisp/emacs-lisp/cl-macs.el
+++ b/lisp/emacs-lisp/cl-macs.el
@@ -1037,9 +1037,10 @@ cl-loop
 
 (defmacro cl--push-clause-loop-body (clause)
   "Apply CLAUSE to both `cl--loop-conditions' and `cl--loop-body'."
-  `(progn
-     (push ,clause cl--loop-conditions)
-     (push ,clause cl--loop-body)))
+  (macroexp-let2 nil sym clause
+    `(progn
+       (push ,sym cl--loop-conditions)
+       (push ,sym cl--loop-body))))
 
 ;; Below is a complete spec for cl-loop, in several parts that correspond
 ;; to the syntax given in CLtL2.  The specs do more than specify where

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In GNU Emacs 28.0.50 (build 21, x86_64-pc-linux-gnu, GTK+ Version 3.24.5, cairo 
version 1.16.0)
 of 2020-02-04 built on calancha-pc.dy.bbexcite.jp
Repository revision: e287da5a8154d83a97107b64915ccc17e3a086b8
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux 10 (buster)