Deprecate memoizable.

activesupport/lib/active_support/memoizable.rb

 require 'active_support/core_ext/kernel/singleton_class'
 require 'active_support/core_ext/module/aliasing'
+require 'active_support/deprecation'
 
 module ActiveSupport
   module Memoizable
+    def self.extended(base)
+      ActiveSupport::Deprecation.warn "ActiveSupport::Memoizable is deprecated and will be removed in future releases," \
+        "simply use Ruby instead.", caller
+      super
+    end
+
     def self.memoized_ivar_for(symbol)
       "@_memoized_#{symbol.to_s.sub(/\?\Z/, '_query').sub(/!\Z/, '_bang')}".to_sym
     end

activesupport/test/flush_cache_on_private_memoization_test.rb

@@ -2,7 +2,9 @@
 require 'test/unit'
 
 class FlashCacheOnPrivateMemoizationTest < Test::Unit::TestCase
-  extend ActiveSupport::Memoizable
+  ActiveSupport::Deprecation.silence do
+    extend ActiveSupport::Memoizable
+  end
 
   def test_public
     assert_method_unmemoizable :pub

activesupport/test/memoizable_test.rb

@@ -2,7 +2,9 @@
 
 class MemoizableTest < ActiveSupport::TestCase
   class Person
-    extend ActiveSupport::Memoizable
+    ActiveSupport::Deprecation.silence do
+      extend ActiveSupport::Memoizable
+    end
 
     attr_reader :name_calls, :age_calls, :is_developer_calls, :name_query_calls
 
@@ -65,7 +67,9 @@ def name
   end
 
   module Rates
-    extend ActiveSupport::Memoizable
+    ActiveSupport::Deprecation.silence do
+      extend ActiveSupport::Memoizable
+    end
 
     attr_reader :sales_tax_calls
     def sales_tax(price)
@@ -77,7 +81,9 @@ def sales_tax(price)
   end
 
   class Calculator
-    extend ActiveSupport::Memoizable
+    ActiveSupport::Deprecation.silence do
+      extend ActiveSupport::Memoizable
+    end
     include Rates
 
     attr_reader :fib_calls
@@ -215,7 +221,9 @@ def test_memoization_with_boolean_arg
 
   def test_object_memoization
     [Company.new, Company.new, Company.new].each do |company|
-      company.extend ActiveSupport::Memoizable
+      ActiveSupport::Deprecation.silence do
+        company.extend ActiveSupport::Memoizable
+      end
       company.memoize :name
 
       assert_equal "37signals", company.name
@@ -249,11 +257,15 @@ def test_object_memoized_module_methods
   def test_double_memoization
     assert_raise(RuntimeError) { Person.memoize :name }
     person = Person.new
-    person.extend ActiveSupport::Memoizable
+    ActiveSupport::Deprecation.silence do
+      person.extend ActiveSupport::Memoizable
+    end
     assert_raise(RuntimeError) { person.memoize :name }
 
     company = Company.new
-    company.extend ActiveSupport::Memoizable
+    ActiveSupport::Deprecation.silence do
+      company.extend ActiveSupport::Memoizable
+    end
     company.memoize :name
     assert_raise(RuntimeError) { company.memoize :name }
   end