Fixed regression with referencing polymorphic assoc in eager-load

This is cased by 03118bc + 9b5d603. The first commit referenced the undefined
local variable `column` when it should be using `reflection.type` as the lookup
key. The second commit changed `build_arel` to not modify the `bind_values` in-
place so we need to combine the arel's `bind_values` with the relation's when
building the SQL.

Fixes #16591

Related #15821 / #15892 / 7aeca50

1 files changed, 10 insertions, 0 deletions

diff --git a/activerecord/test/cases/associations/eager_test.rb b/activerecord/test/cases/associations/eager_test.rb
index 21912fdf0f..b852bd3536 100644
--- a/activerecord/test/cases/associations/eager_test.rb
+++ b/activerecord/test/cases/associations/eager_test.rb
@@ -1290,4 +1290,14 @@ class EagerAssociationTest < ActiveRecord::TestCase
     david = Author.where(id: "1").eager_load(:readonly_comments).first!
     assert david.readonly_comments.first.readonly?
   end
+
+  test "preloading a polymorphic association with references to the associated table" do
+    post = Post.includes(:tags).references(:tags).where('tags.name = ?', 'General').first
+    assert_equal posts(:welcome), post
+  end
+
+  test "eager-loading a polymorphic association with references to the associated table" do
+    post = Post.eager_load(:tags).where('tags.name = ?', 'General').first
+    assert_equal posts(:welcome), post
+  end
 end