From 13dffd8a2a1350c3293ac9e180e3840b9f522e79 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Wed, 18 Jan 2017 03:38:52 +0000
Subject: [PATCH] class.c: non-keyword hash class

* class.c (rb_extract_keywords): keep the class of non-keyword
  elements hash as the original.  [ruby-core:77813] [Bug #12884]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57360 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 class.c                   |  3 +++
 test/ruby/test_keyword.rb | 12 ++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/class.c b/class.c
index 43530c9461..5c54b0c7d4 100644
--- a/class.c
+++ b/class.c
@@ -1841,6 +1841,9 @@ rb_extract_keywords(VALUE *orighash)
     }
     st_foreach(rb_hash_tbl_raw(hash), separate_symbol, (st_data_t)&parthash);
     *orighash = parthash[1];
+    if (parthash[1] && RBASIC_CLASS(hash) != rb_cHash) {
+	RBASIC_SET_CLASS(parthash[1], RBASIC_CLASS(hash));
+    }
     return parthash[0];
 }
 
diff --git a/test/ruby/test_keyword.rb b/test/ruby/test_keyword.rb
index ad0bf63492..f10412e6cd 100644
--- a/test/ruby/test_keyword.rb
+++ b/test/ruby/test_keyword.rb
@@ -629,4 +629,16 @@ class TestKeywordArguments < Test::Unit::TestCase
       klass.new(d: 4)
     end
   end
+
+  def test_non_keyword_hash_subclass
+    bug12884 = '[ruby-core:77813] [Bug #12884]'
+    klass = EnvUtil.labeled_class("Child", Hash)
+    obj = Object.new
+    def obj.t(params = klass.new, d: nil); params; end
+    x = klass.new
+    x["foo"] = "bar"
+    result = obj.t(x)
+    assert_equal(x, result)
+    assert_kind_of(klass, result, bug12884)
+  end
 end