From 76f50fa55ce19eb4ae0a249a53289c724ea23492 Mon Sep 17 00:00:00 2001
From: Dmitry Gutov
Date: Tue, 16 Sep 2025 02:14:09 +0300
Subject: ruby-syntax-propertize: Add exception for /=

* lisp/progmodes/ruby-mode.el (ruby-syntax-propertize):
Create an exception for assign-division operator not to be
recognized as regexp start (bug#79454).

* test/lisp/progmodes/ruby-mode-resources/ruby.rb: Add example.
---
 lisp/progmodes/ruby-mode.el                     | 1 +
 test/lisp/progmodes/ruby-mode-resources/ruby.rb | 1 +
 2 files changed, 2 insertions(+)

diff --git a/lisp/progmodes/ruby-mode.el b/lisp/progmodes/ruby-mode.el
index 459f8f338f7..b1104bf88a0 100644
--- a/lisp/progmodes/ruby-mode.el
+++ b/lisp/progmodes/ruby-mode.el
@@ -2204,6 +2204,7 @@ A slash character after any of these should begin a regexp."))
                         (or (not
                              ;; Looks like division.
                              (or (eql (char-after) ?\s)
+                                 (eql (char-after) ?=)
                                  (not (eql (char-before (1- (point))) ?\s))))
                             (save-excursion
                               (forward-char -1)
diff --git a/test/lisp/progmodes/ruby-mode-resources/ruby.rb b/test/lisp/progmodes/ruby-mode-resources/ruby.rb
index a411b39a8fc..4fa7332f017 100644
--- a/test/lisp/progmodes/ruby-mode-resources/ruby.rb
+++ b/test/lisp/progmodes/ruby-mode-resources/ruby.rb
@@ -39,6 +39,7 @@ a = sub / aslb + bsub / bslb;
 
 # Highlight the regexp after "if".
 x = toto / foo if / do bar/ =~ "dobar"
+x /= 4
 
 # Regexp options are highlighted.
 
-- 
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