fix inverse_of association in block of new child

This fixes inconsistency when building children of association
which has inverse_of set properly.

When creating new association object with a block:

    parent.association.build do |child|
      child.parent.equal?(parent) # false
    end

So the block the `child.parent` did not point to the same object.
But when the object is created it points to same instance:

    child = parent.association.build
    child.parent.equal?(parent) # true

1 files changed, 16 insertions, 0 deletions

diff --git a/activerecord/test/cases/associations/inverse_associations_test.rb b/activerecord/test/cases/associations/inverse_associations_test.rb
index c8cad84013..36f1e633ed 100644
--- a/activerecord/test/cases/associations/inverse_associations_test.rb
+++ b/activerecord/test/cases/associations/inverse_associations_test.rb
@@ -235,6 +235,22 @@ class InverseHasManyTests < ActiveRecord::TestCase
     assert_equal m.name, i.man.name, "Name of man should be the same after changes to newly-created-child-owned instance"
   end
 
+  def test_parent_instance_should_be_shared_within_create_block_of_new_child
+    man = Man.first
+    interest = man.interests.build do |i|
+      assert i.man.equal?(man), "Man of child should be the same instance as a parent"
+    end
+    assert interest.man.equal?(man), "Man of the child should still be the same instance as a parent"
+  end
+
+  def test_parent_instance_should_be_shared_within_build_block_of_new_child
+    man = Man.first
+    interest = man.interests.build do |i|
+      assert i.man.equal?(man), "Man of child should be the same instance as a parent"
+    end
+    assert interest.man.equal?(man), "Man of the child should still be the same instance as a parent"
+  end
+
   def test_parent_instance_should_be_shared_with_poked_in_child
     m = men(:gordon)
     i = Interest.create(:topic => 'Industrial Revolution Re-enactment')