Remove NilClass whiners feature.

Removing this feature causes boost in performance when using Ruby 1.9.

Ruby 1.9 started to do implicit conversions using `to_ary` and `to_str`
in some STDLIB methods (like Array#join). To do such implicit conversions,
Ruby 1.9 always dispatches the method and rescues the NoMethodError exception
in case one is raised.

Therefore, since the whiners feature defined NilClass#method_missing, such
implicit conversions for nil became much, much slower. In fact, just defining
NilClass#method_missing (even without the whiners feature) already causes a
massive slow down. Here is a snippet that shows such slow down:

    require "benchmark"
    Benchmark.realtime { 1_000.times { [nil,nil,nil].join } }

    class NilClass
      def method_missing(*args)
        raise NoMethodError
      end
    end

    Benchmark.realtime { 1_000.times { [nil,nil,nil].join } }

2 files changed, 2 insertions, 83 deletions

diff --git a/activesupport/lib/active_support/whiny_nil.rb b/activesupport/lib/active_support/whiny_nil.rb
index 577db5018e..a065233679 100644
--- a/activesupport/lib/active_support/whiny_nil.rb
+++ b/activesupport/lib/active_support/whiny_nil.rb
@@ -1,21 +1,6 @@
 # Extensions to +nil+ which allow for more helpful error messages for people who
 # are new to Rails.
 #
-# Ruby raises NoMethodError if you invoke a method on an object that does not
-# respond to it:
-#
-#   $ ruby -e nil.destroy
-#   -e:1: undefined method `destroy' for nil:NilClass (NoMethodError)
-#
-# With these extensions, if the method belongs to the public interface of the
-# classes in NilClass::WHINERS the error message suggests which could be the
-# actual intended class:
-#
-#   $ rails runner nil.destroy
-#   ...
-#   You might have expected an instance of ActiveRecord::Base.
-#   ...
-#
 # NilClass#id exists in Ruby 1.8 (though it is deprecated). Since +id+ is a fundamental
 # method of Active Record models NilClass#id is redefined as well to raise a RuntimeError
 # and warn the user. She probably wanted a model database identifier and the 4
@@ -25,36 +10,13 @@
 # By default it is on in development and test modes, and it is off in production
 # mode.
 class NilClass
-  METHOD_CLASS_MAP = Hash.new
-
   def self.add_whiner(klass)
-    methods = klass.public_instance_methods - public_instance_methods
-    class_name = klass.name
-    methods.each { |method| METHOD_CLASS_MAP[method.to_sym] = class_name }
+    ActiveSupport::Deprecation.warn "NilClass.add_whiner is deprecated and this functionality is " \
+      "removed from Rails versions as it affects Ruby 1.9 performance.", caller
   end
 
-  add_whiner ::Array
-
   # Raises a RuntimeError when you attempt to call +id+ on +nil+.
   def id
     raise RuntimeError, "Called id for nil, which would mistakenly be #{object_id} -- if you really wanted the id of nil, use object_id", caller
   end
-
-  private
-    def method_missing(method, *args)
-      if klass = METHOD_CLASS_MAP[method]
-        raise_nil_warning_for klass, method, caller
-      else
-        super
-      end
-    end
-
-    # Raises a NoMethodError when you attempt to call a method on +nil+.
-    def raise_nil_warning_for(class_name = nil, selector = nil, with_caller = nil)
-      message = "You have a nil object when you didn't expect it!"
-      message << "\nYou might have expected an instance of #{class_name}." if class_name
-      message << "\nThe error occurred while evaluating nil.#{selector}" if selector
-
-      raise NoMethodError, message, with_caller || caller
-    end
 end
diff --git a/activesupport/test/whiny_nil_test.rb b/activesupport/test/whiny_nil_test.rb
index 1acaf7228f..8c1f1b2677 100644
--- a/activesupport/test/whiny_nil_test.rb
+++ b/activesupport/test/whiny_nil_test.rb
@@ -1,54 +1,11 @@
-# Stub to enable testing without Active Record
-module ActiveRecord
-  class Base
-    def save!
-    end
-  end
-end
-
 require 'abstract_unit'
 require 'active_support/whiny_nil'
 
-NilClass.add_whiner ::ActiveRecord::Base
-
 class WhinyNilTest < Test::Unit::TestCase
-  def test_unchanged
-    nil.method_thats_not_in_whiners
-  rescue NoMethodError => nme
-    assert_match(/nil:NilClass/, nme.message)
-  end
-
-  def test_active_record
-    nil.save!
-  rescue NoMethodError => nme
-    assert_no_match(/nil:NilClass/, nme.message)
-    assert_match(/nil\.save!/, nme.message)
-  end
-
-  def test_array
-    nil.each
-  rescue NoMethodError => nme
-    assert_no_match(/nil:NilClass/, nme.message)
-    assert_match(/nil\.each/, nme.message)
-  end
-
   def test_id
     nil.id
   rescue RuntimeError => nme
     assert_no_match(/nil:NilClass/, nme.message)
     assert_match(Regexp.new(nil.object_id.to_s), nme.message)
   end
-
-  def test_no_to_ary_coercion
-    nil.to_ary
-  rescue NoMethodError => nme
-    assert_no_match(/nil:NilClass/, nme.message)
-    assert_match(/nil\.to_ary/, nme.message)
-  end
-
-  def test_no_to_str_coercion
-    nil.to_str
-  rescue NoMethodError => nme
-    assert_match(/nil:NilClass/, nme.message)
-  end
 end