Not really worth having the HasAssociation module for just a single method

activerecord/lib/active_record/associations.rb

@@ -120,7 +120,6 @@ module Associations # :nodoc:
     # So there is no need to eager load them.
     autoload :AssociationCollection, 'active_record/associations/association_collection'
     autoload :AssociationProxy, 'active_record/associations/association_proxy'
-    autoload :HasAssociation, 'active_record/associations/has_association'
     autoload :ThroughAssociation, 'active_record/associations/through_association'
     autoload :BelongsToAssociation, 'active_record/associations/belongs_to_association'
     autoload :BelongsToPolymorphicAssociation, 'active_record/associations/belongs_to_polymorphic_association'

activerecord/lib/active_record/associations/association_collection.rb

@@ -18,8 +18,6 @@ module Associations
     # If you need to work on all current children, new and existing records,
     # +load_target+ and the +loaded+ flag are your friends.
     class AssociationCollection < AssociationProxy #:nodoc:
-      include HasAssociation
-
       delegate :group, :order, :limit, :joins, :where, :preload, :eager_load, :includes, :from, :lock, :readonly, :having, :to => :scoped
 
       def select(select = nil)

activerecord/lib/active_record/associations/association_proxy.rb

@@ -9,11 +9,11 @@ module Associations
     #   AssociationProxy
     #     BelongsToAssociation
     #       BelongsToPolymorphicAssociation
-    #     AssociationCollection + HasAssociation
+    #     AssociationCollection
     #       HasAndBelongsToManyAssociation
     #       HasManyAssociation
     #         HasManyThroughAssociation + ThroughAssociation
-    #     HasOneAssociation + HasAssociation
+    #     HasOneAssociation
     #       HasOneThroughAssociation + ThroughAssociation
     #
     # Association proxies in Active Record are middlemen between the object that
@@ -252,6 +252,13 @@ def construct_owner_conditions(table = aliased_table, reflection = @reflection)
           table.create_and(conditions)
         end
 
+        # Sets the owner attributes on the given record
+        def set_owner_attributes(record)
+          if @owner.persisted?
+            construct_owner_attributes.each { |key, value| record[key] = value }
+          end
+        end
+
       private
         # Forwards any missing method call to the \target.
         def method_missing(method, *args)

activerecord/lib/active_record/associations/has_association.rb

-module ActiveRecord
-  module Associations
-    # Included in all has_* associations (i.e. everything except belongs_to)
-    module HasAssociation #:nodoc:
-      protected
-        # Sets the owner attributes on the given record
-        def set_owner_attributes(record)
-          if @owner.persisted?
-            construct_owner_attributes.each { |key, value| record[key] = value }
-          end
-        end
-    end
-  end
-end

activerecord/lib/active_record/associations/has_one_association.rb

@@ -2,8 +2,6 @@ module ActiveRecord
   # = Active Record Belongs To Has One Association
   module Associations
     class HasOneAssociation < AssociationProxy #:nodoc:
-      include HasAssociation
-
       def create(attrs = {})
         new_record do |reflection|
           attrs = merge_with_conditions(attrs)