bug#46912: 28.0.50; Byte compiled defvar with lexical binding throws (void-variable foo)

[Pip Cet <pipcet@gmail.com>]

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On Thu, Mar 4, 2021 at 11:15 PM Joseph Mingrone <jrm@ftfl.ca> wrote:
> With this patch applied to 20596a5, I still see the problems Vitalie
> reported.

Strange, I don't see how I managed to convince myself it works here.
Anyway, this should work.

Pip

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From 09a195ed2ed7004c54d1701d0017a4fb10f6cbce Mon Sep 17 00:00:00 2001
From: Pip Cet <pipcet@gmail.com>
Date: Thu, 4 Mar 2021 21:06:13 +0000
Subject: [PATCH] Don't ignore lexically-bound variables in a defvar
 (bug#46912)

* lisp/emacs-lisp/byte-opt.el (byte-optimize-form-code-walker): Walk
the value form of a defvar.
---
 lisp/emacs-lisp/byte-opt.el | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lisp/emacs-lisp/byte-opt.el b/lisp/emacs-lisp/byte-opt.el
index b51ba801552d6..b3325816c5c97 100644
--- a/lisp/emacs-lisp/byte-opt.el
+++ b/lisp/emacs-lisp/byte-opt.el
@@ -607,9 +607,12 @@ byte-optimize-form-code-walker
            (setq args (cddr args)))
          (cons fn (nreverse var-expr-list))))
 
-      (`(defvar ,(and (pred symbolp) name) . ,_)
-       (push name byte-optimize--dynamic-vars)
-       form)
+      (`(defvar ,(and (pred symbolp) name) . ,rest)
+       (let ((optimized-rest (and rest
+                                  (cons (byte-optimize-form (car rest) nil)
+                                        (cdr rest)))))
+         (push name byte-optimize--dynamic-vars)
+         `(defvar ,name . ,optimized-rest)))
 
       (`(,(pred byte-code-function-p) . ,exps)
        (cons fn (mapcar #'byte-optimize-form exps)))
-- 
2.30.1