Don't rewrite `set` to `setq` of lexical variables

Only perform the rewrite

   (set 'VAR X) -> (setq VAR X)

for dynamic variables, as `set` isn't supposed to affect
lexical vars (and never does so when interpreted).

* lisp/emacs-lisp/byte-opt.el (byte-optimize-set):
* test/lisp/emacs-lisp/bytecomp-tests.el (bytecomp-tests--xx): New.
(bytecomp-tests--test-cases): Add test cases.
* test/lisp/emacs-lisp/bytecomp-resources/warn-variable-set-nonvariable.el:
Remove obsolete test.

1 files changed, 10 insertions, 9 deletions

diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index 0d5f8c26eb2..4ef9cb0a1e4 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -1531,15 +1531,16 @@ See Info node `(elisp) Integer Basics'."
 
 (put 'set 'byte-optimizer #'byte-optimize-set)
 (defun byte-optimize-set (form)
-  (let ((var (car-safe (cdr-safe form))))
-    (cond
-     ((and (eq (car-safe var) 'quote) (consp (cdr var)))
-      `(setq ,(cadr var) ,@(cddr form)))
-     ((and (eq (car-safe var) 'make-local-variable)
-	   (eq (car-safe (setq var (car-safe (cdr var)))) 'quote)
-	   (consp (cdr var)))
-      `(progn ,(cadr form) (setq ,(cadr var) ,@(cddr form))))
-     (t form))))
+  (pcase (cdr form)
+    ;; Make sure we only turn `set' into `setq' for dynamic variables.
+    (`((quote ,(and var (guard (and (symbolp var)
+                                    (not (macroexp--const-symbol-p var))
+                                    (not (assq var byte-optimize--lexvars))))))
+       ,newval)
+     `(setq ,var ,newval))
+    (`(,(and ml `(make-local-variable ,(and v `(quote ,_)))) ,newval)
+     `(progn ,ml (,(car form) ,v ,newval)))
+    (_ form)))
 
 ;; enumerating those functions which need not be called if the returned
 ;; value is not used.  That is, something like