Fixed #36155 -- Improved error handling when annotate arguments require an alias.

Regression in ed0cbc8d8b.

tests/annotations/tests.py

@@ -969,6 +969,24 @@ class NonAggregateAnnotationTestCase(TestCase):
         ):
             Book.objects.annotate(BooleanField(), Value(False), is_book=True)
 
+    def test_complex_annotations_must_have_an_alias(self):
+        complex_annotations = [
+            F("rating") * F("price"),
+            Value("title"),
+            Case(When(pages__gte=400, then=Value("Long")), default=Value("Short")),
+            Subquery(
+                Book.objects.filter(publisher_id=OuterRef("pk"))
+                .order_by("-pubdate")
+                .values("name")[:1]
+            ),
+            Exists(Book.objects.filter(publisher_id=OuterRef("pk"))),
+        ]
+        msg = "Complex annotations require an alias"
+        for annotation in complex_annotations:
+            with self.subTest(annotation=annotation):
+                with self.assertRaisesMessage(TypeError, msg):
+                    Book.objects.annotate(annotation)
+
     def test_chaining_annotation_filter_with_m2m(self):
         qs = (
             Author.objects.filter(