[Bug #21331] Prohibit hash modification during stlike loop

1 files changed, 8 insertions, 0 deletions

diff --git a/test/ruby/test_hash.rb b/test/ruby/test_hash.rb
index b6c18ea958..76af5b6183 100644
--- a/test/ruby/test_hash.rb
+++ b/test/ruby/test_hash.rb
@@ -1853,6 +1853,14 @@ class TestHash < Test::Unit::TestCase
       end
     end
     assert_equal(@cls[a: 2, b: 2, c: 3, d: 4, e: 5, f: 6, g: 7, h: 8, i: 9, j: 10], x)
+
+    x = (1..1337).to_h {|k| [k, k]}
+    assert_raise_with_message(RuntimeError, /rehash during iteration/) do
+      x.transform_values! {|v|
+        x.rehash if v == 1337
+        v * 2
+      }
+    end
   end
 
   def hrec h, n, &b