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.

2 files changed, 12 insertions, 6 deletions

diff --git a/test/lisp/emacs-lisp/bytecomp-resources/warn-variable-set-nonvariable.el b/test/lisp/emacs-lisp/bytecomp-resources/warn-variable-set-nonvariable.el
deleted file mode 100644
index 0c76c4d388b..00000000000
--- a/test/lisp/emacs-lisp/bytecomp-resources/warn-variable-set-nonvariable.el
+++ /dev/null
@@ -1,3 +0,0 @@
-;;; -*- lexical-binding: t -*-
-(defun foo ()
-  (set '(a) nil))
diff --git a/test/lisp/emacs-lisp/bytecomp-tests.el b/test/lisp/emacs-lisp/bytecomp-tests.el
index 1ca44dc7a48..e7c308213e4 100644
--- a/test/lisp/emacs-lisp/bytecomp-tests.el
+++ b/test/lisp/emacs-lisp/bytecomp-tests.el
@@ -59,6 +59,8 @@ inner loops respectively."
        (setq i (1- i)))
      res))
 
+(defvar bytecomp-tests--xx nil)
+
 (defconst bytecomp-tests--test-cases
   '(
     ;; some functional tests
@@ -692,6 +694,16 @@ inner loops respectively."
            (f (lambda ()
                 (let ((y x)) (list y 3 y)))))
       (funcall f))
+
+    ;; Test rewriting of `set' to `setq' (only done on dynamic variables).
+    (let ((xx 1)) (set 'xx 2) xx)
+    (let ((bytecomp-tests--xx 1))
+      (set 'bytecomp-tests--xx 2)
+      bytecomp-tests--xx)
+    (let ((aaa 1)) (set (make-local-variable 'aaa) 2) aaa)
+    (let ((bytecomp-tests--xx 1))
+      (set (make-local-variable 'bytecomp-tests--xx) 2)
+      bytecomp-tests--xx)
     )
   "List of expressions for cross-testing interpreted and compiled code.")
 
@@ -953,9 +965,6 @@ byte-compiled.  Run with dynamic binding."
 (bytecomp--define-warning-file-test "warn-variable-set-constant.el"
                             "attempt to set constant")
 
-(bytecomp--define-warning-file-test "warn-variable-set-nonvariable.el"
-                            "variable reference to nonvariable")
-
 (bytecomp--define-warning-file-test "warn-variable-setq-nonvariable.el"
                             "attempt to set non-variable")