* test/ruby/test_basicinstructions.rb: add a test to check access

  instance variables on special const objects.

  All of such objects are frozen, so that we can not set instance
  variables for them. But we can read instance variables and return
  default value (nil).


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54556 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 31 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 7f39aeed38..995c9eb60a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Wed Apr 13 12:00:08 2016  Koichi Sasada  <ko1@atdot.net>
+
+	* test/ruby/test_basicinstructions.rb: add a test to check access
+	  instance variables on special const objects.
+
+	  All of such objects are frozen, so that we can not set instance
+	  variables for them. But we can read instance variables and return
+	  default value (nil).
+
 Tue Apr 12 20:40:35 2016  Kaneko Yuichiro  <spiketeika@gmail.com>
 
 	* ext/date/date_core.c (time_to_time): should preserve timezone
diff --git a/test/ruby/test_basicinstructions.rb b/test/ruby/test_basicinstructions.rb
index d13c41c276..c0ce02648d 100644
--- a/test/ruby/test_basicinstructions.rb
+++ b/test/ruby/test_basicinstructions.rb
@@ -698,4 +698,26 @@ class TestBasicInstructions < Test::Unit::TestCase
     assert_equal [], [*a]
     assert_equal [1], [1, *a]
   end
+
+  def test_special_const_instance_variables
+    assert_separately(%w(-W0), <<-INPUT, timeout: 60)
+    module M
+      def get
+        # we can not set instance variables on special const objects.
+        # However, we can access instance variables with default value (nil).
+        @ivar
+      end
+    end
+    class Fixnum; include M; end
+    class Float; include M; end
+    class Symbol; include M; end
+    class FalseClass; include M; end
+    class TrueClass; include M; end
+    class NilClass; include M; end
+
+    [123, 1.2, :sym, false, true, nil].each{|obj|
+      assert_equal(nil, obj.get)
+    }
+    INPUT
+  end
 end