Work around frozen Date memoization

activesupport/lib/active_support/core_ext/date/behavior.rb

@@ -7,6 +7,22 @@ module ActiveSupport #:nodoc:
         def acts_like_date?
           true
         end
+
+        # Date memoizes some instance methods using metaprogramming to wrap
+        # the methods with one that caches the result in an instance variable.
+        # If a Date is frozen but the memoized method hasn't been called, the
+        # first call will result in a frozen object error since the memo
+        # instance variable is uninitialized. Work around by eagerly memoizing
+        # before freezing.
+        def freeze #:nodoc:
+          self.class.private_instance_methods(false).each do |m|
+            if m.to_s =~ /\A__\d+__\Z/
+              instance_variable_set(:"@#{m}", [send(m)])
+            end
+          end
+
+          super
+        end
       end
     end
   end

activesupport/test/core_ext/date_ext_test.rb

@@ -198,10 +198,6 @@ class DateExtCalculationsTest < Test::Unit::TestCase
     assert_equal Time.local(2005,2,21,23,59,59), Date.new(2005,2,21).end_of_day
   end
 
-  def test_date_acts_like_date
-    assert Date.new.acts_like_date?
-  end
-
   def test_xmlschema
     with_env_tz 'US/Eastern' do
       assert_match(/^1980-02-28T00:00:00-05:?00$/, Date.new(1980, 2, 28).xmlschema)
@@ -245,3 +241,15 @@ class DateExtCalculationsTest < Test::Unit::TestCase
       old_tz ? ENV['TZ'] = old_tz : ENV.delete('TZ')
     end
 end
+
+class DateExtBehaviorTest < Test::Unit::TestCase
+  def test_date_acts_like_date
+    assert Date.new.acts_like_date?
+  end
+
+  def test_freeze_doesnt_clobber_memoized_instance_methods
+    assert_nothing_raised do
+      Date.today.freeze.inspect
+    end
+  end
+end