* array.c (flatten): use rb_obj_class instead of rb_class_of

  because rb_class_of may return a singleton class.
  [ruby-dev:49781] [Bug #12738]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@56111 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 25 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index 39eb848292..3fe44c32d6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Sep  8 17:47:18 2016  Kazuki Tsujimoto  <kazuki@callcc.net>
+
+	* array.c (flatten): use rb_obj_class instead of rb_class_of
+	  because rb_class_of may return a singleton class.
+	  [ruby-dev:49781] [Bug #12738]
+
 Thu Sep  8 17:40:15 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* tool/rbinstall.rb (gem): use the bindir of each gemspec instead
diff --git a/array.c b/array.c
index 65fd0b6268..4e60177121 100644
--- a/array.c
+++ b/array.c
@@ -4583,7 +4583,7 @@ flatten(VALUE ary, int level, int *modified)
 
     st_free_table(memo);
 
-    RBASIC_SET_CLASS(result, rb_class_of(ary));
+    RBASIC_SET_CLASS(result, rb_obj_class(ary));
     return result;
 }
 
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index addce0d9ba..a19e22aab4 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -813,6 +813,15 @@ class TestArray < Test::Unit::TestCase
     assert_nothing_raised(RuntimeError, bug10748) {a.flatten(1)}
   end
 
+  def test_flattern_singleton_class
+    bug12738 = '[ruby-dev:49781] [Bug #12738]'
+    a = [[0]]
+    class << a
+      def m; end
+    end
+    assert_raise(NoMethodError, bug12738) { a.flatten.m }
+  end
+
   def test_flatten!
     a1 = @cls[ 1, 2, 3]
     a2 = @cls[ 5, 6 ]
@@ -850,6 +859,15 @@ class TestArray < Test::Unit::TestCase
     assert_nothing_raised(RuntimeError, bug10748) {a.flatten!(1)}
   end
 
+  def test_flattern_singleton_class!
+    bug12738 = '[ruby-dev:49781] [Bug #12738]'
+    a = [[0]]
+    class << a
+      def m; end
+    end
+    assert_nothing_raised(NameError, bug12738) { a.flatten!.m }
+  end
+
   def test_flatten_with_callcc
     need_continuation
     o = Object.new