Optimise 'while' bodies for effect

* lisp/emacs-lisp/byte-opt.el (byte-optimize-form-code-walker):
Treat all expressions in the body of 'while' as for-effect,
since their values are discarded.  This also finds some errors.

1 files changed, 7 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index 22fea1b8da9..07fd548dec2 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -480,6 +480,13 @@
                                                  backwards)))))
              (cons fn (mapcar 'byte-optimize-form (cdr form)))))
 
+          ((eq fn 'while)
+           (unless (consp (cdr form))
+             (byte-compile-warn "too few arguments for `while'"))
+           (cons fn
+                 (cons (byte-optimize-form (cadr form) nil)
+                       (byte-optimize-body (cddr form) t))))
+
           ((eq fn 'interactive)
            (byte-compile-warn "misplaced interactive spec: `%s'"
                               (prin1-to-string form))