Fix hm:t to self table aliasing in construct_scope

activerecord/lib/active_record/associations/through_association_scope.rb

@@ -21,9 +21,17 @@ module ActiveRecord
         construct_owner_attributes(@reflection)
       end
 
+      def aliased_through_table
+        name = @reflection.through_reflection.table_name
+
+        @reflection.table_name == name ?
+          @reflection.through_reflection.klass.arel_table.alias(name + "_join") :
+          @reflection.through_reflection.klass.arel_table
+      end
+
       # Build SQL conditions from attributes, qualified by table name.
       def construct_conditions
-        table = @reflection.through_reflection.klass.arel_table
+        table = aliased_through_table
         conditions = construct_quoted_owner_attributes(@reflection.through_reflection).map do |attr, value|
           table[attr].eq(value)
         end
@@ -53,7 +61,7 @@ module ActiveRecord
       end
 
       def construct_joins
-        right = @reflection.through_reflection.klass.arel_table
+        right = aliased_through_table
         left  = @reflection.klass.arel_table
 
         conditions = []

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -392,7 +392,7 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
     sarah = Person.create!(:first_name => 'Sarah', :primary_contact_id => people(:susan).id, :gender => 'F', :number1_fan_id => 1)
     john = Person.create!(:first_name => 'John', :primary_contact_id => sarah.id, :gender => 'M', :number1_fan_id => 1)
     assert_equal sarah.agents, [john]
-    assert_equal people(:susan).agents_of_agents, [john]
+    assert_equal people(:susan).agents.map(&:agents).flatten, people(:susan).agents_of_agents
   end
 
   def test_collection_singular_ids_getter_with_string_primary_keys

activerecord/test/models/person.rb

@@ -12,6 +12,7 @@ class Person < ActiveRecord::Base
 
   belongs_to :primary_contact, :class_name => 'Person'
   has_many :agents, :class_name => 'Person', :foreign_key => 'primary_contact_id'
+  has_many :agents_of_agents, :through => :agents, :source => :agents
   belongs_to :number1_fan, :class_name => 'Person'
 
   scope :males, :conditions => { :gender => 'M' }