[1.9.x] Fixed #26373 -- Fixed reverse lookup crash with a ForeignKey to_field in a subquery.

Backport of 4c1c93032f4a015cbb4b33958603d18ac43515b4 from master

django/db/models/query.py

@@ -1113,7 +1113,7 @@ class QuerySet(object):
             # if they are set up to select only a single field.
             if len(self._fields or self.model._meta.concrete_fields) > 1:
                 raise TypeError('Cannot use multi-field values as a filter value.')
-        else:
+        elif self.model != field.model:
             # If the query is used as a subquery for a ForeignKey with non-pk
             # target field, make sure to select the target field in the subquery.
             foreign_fields = getattr(field, 'foreign_related_fields', ())

docs/releases/1.9.5.txt

@@ -30,3 +30,7 @@ Bugfixes
 
 * Fixed a regression that caused ``collectstatic --clear`` to fail if the
   storage doesn't implement ``path()`` (:ticket:`26297`).
+
+* Fixed a crash when using a reverse lookup with a subquery when a
+  ``ForeignKey`` has a ``to_field`` set to something other than the primary key
+  (:ticket:`26373`).

tests/queries/tests.py

@@ -2474,6 +2474,10 @@ class ToFieldTests(TestCase):
             set(Eaten.objects.filter(food__in=Food.objects.filter(name='apple').values('eaten__meal'))),
             set()
         )
+        self.assertEqual(
+            set(Food.objects.filter(eaten__in=Eaten.objects.filter(meal='lunch'))),
+            {apple}
+        )
 
     def test_reverse_in(self):
         apple = Food.objects.create(name="apple")