lib/ostruct.rb: Fix returned value of each_pair.

From a patch by Marcus Stollsteimer. [Fixes #13169]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57515 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/ostruct.rb

@@ -130,6 +130,7 @@ class OpenStruct
   def each_pair
     return to_enum(__method__) { @table.size } unless block_given?
     @table.each_pair{|p| yield p}
+    self
   end
 
   #

test/ostruct/test_ostruct.rb

@@ -141,6 +141,7 @@ class TC_OpenStruct < Test::Unit::TestCase
   def test_each_pair
     h = {name: "John Smith", age: 70, pension: 300}
     os = OpenStruct.new(h)
+    assert_same os, os.each_pair{ }
     assert_equal '#<Enumerator: #<OpenStruct name="John Smith", age=70, pension=300>:each_pair>', os.each_pair.inspect
     assert_equal [[:name, "John Smith"], [:age, 70], [:pension, 300]], os.each_pair.to_a
     assert_equal 3, os.each_pair.size