From 1a16b6ffc2d48b93c730cd6e57fac6a68fa05737 Mon Sep 17 00:00:00 2001
From: Kouhei Yanagita <yanagi@shakenbu.org>
Date: Thu, 27 Jan 2022 14:37:48 +0900
Subject: [PATCH] Make Range#reverse_each raise TypeError if endless

---
 range.c                 | 5 +++++
 test/ruby/test_range.rb | 8 ++++++++
 2 files changed, 13 insertions(+)

diff --git a/range.c b/range.c
index 91c0d2783c..9e55e89c5f 100644
--- a/range.c
+++ b/range.c
@@ -1133,6 +1133,11 @@ range_reverse_each(VALUE range)
     VALUE end = RANGE_END(range);
     int excl = EXCL(range);
 
+    if (NIL_P(end)) {
+        rb_raise(rb_eTypeError, "can't iterate from %s",
+                 rb_obj_classname(end));
+    }
+
     if (FIXNUM_P(beg) && FIXNUM_P(end)) {
         if (excl) {
             if (end == LONG2FIX(FIXNUM_MIN)) return range;
diff --git a/test/ruby/test_range.rb b/test/ruby/test_range.rb
index 5e3dbb349e..bda206d766 100644
--- a/test/ruby/test_range.rb
+++ b/test/ruby/test_range.rb
@@ -582,6 +582,14 @@ class TestRange < Test::Unit::TestCase
     assert_equal([fmin-2, fmin-3], a)
   end
 
+  def test_reverse_each_for_endless_range
+    assert_raise(TypeError) { (1..).reverse_each {} }
+
+    enum = nil
+    assert_nothing_raised { enum = (1..).reverse_each }
+    assert_raise(TypeError) { enum.each {} }
+  end
+
   def test_reverse_each_for_single_point_range
     fmin = RbConfig::LIMITS['FIXNUM_MIN']
     fmax = RbConfig::LIMITS['FIXNUM_MAX']