encoding.c: check external encoding

* encoding.c (rb_enc_get_index): external encoding may not be Data
  object.  [ruby-core:89016] [Bug #15122]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64753 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 7 insertions, 0 deletions

diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 27077b425b..eeda96c9ef 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -3855,4 +3855,11 @@ __END__
       th.join
     end;
   end
+
+  def test_external_encoding_index
+    IO.pipe {|r, w|
+      assert_raise(TypeError) {Marshal.dump(r)}
+      assert_raise(TypeError) {Marshal.dump(w)}
+    }
+  end
 end