Check Module#ruby2_keywords arity

It is considered a mistake, because calling this method with no
arguments has no effect.

1 files changed, 6 insertions, 0 deletions

diff --git a/test/ruby/test_keyword.rb b/test/ruby/test_keyword.rb
index bbf3953c17..c3a3a450f1 100644
--- a/test/ruby/test_keyword.rb
+++ b/test/ruby/test_keyword.rb
@@ -2724,6 +2724,12 @@ class TestKeywordArguments < Test::Unit::TestCase
   end
 
   def test_ruby2_keywords
+    assert_raise(ArgumentError) do
+      Class.new do
+        ruby2_keywords
+      end
+    end
+
     c = Class.new do
       ruby2_keywords def foo(meth, *args)
         send(meth, *args)