Make Range#reverse_each raise TypeError if endless

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;

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']