Refs #32858, Refs #32392 -- Restored using :: shortcut syntax in Cast() on PostgreSQL.

This partly reverts commit fdfbc66331
unnecessary since b69b0c3fe8.

tests/db_functions/comparison/test_cast.py

@@ -1,9 +1,11 @@
 import datetime
 import decimal
+import unittest
 
 from django.db import connection, models
 from django.db.models.functions import Cast
 from django.test import TestCase, ignore_warnings, skipUnlessDBFeature
+from django.test.utils import CaptureQueriesContext
 
 from ..models import Author, DTModel, Fan, FloatModel
 
@@ -125,5 +127,20 @@ class CastTests(TestCase):
         self.assertIsInstance(cast_float, float)
         self.assertEqual(cast_float, 0.125)
 
+    @unittest.skipUnless(connection.vendor == 'postgresql', 'PostgreSQL test')
+    def test_expression_wrapped_with_parentheses_on_postgresql(self):
+        """
+        The SQL for the Cast expression is wrapped with parentheses in case
+        it's a complex expression.
+        """
+        with CaptureQueriesContext(connection) as captured_queries:
+            list(Author.objects.annotate(
+                cast_float=Cast(models.Avg('age'), models.FloatField()),
+            ))
+        self.assertIn(
+            '(AVG("db_functions_author"."age"))::double precision',
+            captured_queries[0]['sql'],
+        )
+
     def test_cast_to_text_field(self):
         self.assertEqual(Author.objects.values_list(Cast('age', models.TextField()), flat=True).get(), '1')