Raise an error when an aggregation references another aggregation of …

…the same call

django/db/models/query.py

@@ -386,8 +386,15 @@ def aggregate(self, *args, **kwargs):
         query = self.query.chain()
         for (alias, aggregate_expr) in kwargs.items():
             query.add_annotation(aggregate_expr, alias, is_summary=True)
-            if not query.annotations[alias].contains_aggregate:
+            annotation = query.annotations[alias]
+            if not annotation.contains_aggregate:
                 raise TypeError("%s is not an aggregate expression" % alias)
+            for expr in annotation.get_source_expressions():
+                if expr.contains_aggregate and hasattr(expr, 'refs') and expr.refs in kwargs:
+                    name = expr.refs
+                    raise exceptions.FieldError("Cannot compute %s('%s'): '%s' is an aggregate" % (
+                        annotation.name, name, name))
+
         return query.get_aggregation(self.db, kwargs)
 
     def count(self):

tests/aggregation/tests.py

@@ -1004,6 +1004,11 @@ def test_annotate_over_annotate(self):
 
         self.assertEqual(author.sum_age, other_author.sum_age)
 
+    def test_aggregate_referencing_aggregate(self):
+        msg = "Cannot compute Avg('age'): 'age' is an aggregate"
+        with self.assertRaisesMessage(FieldError, msg):
+            Author.objects.annotate(age_alias=F('age')).aggregate(age=Sum(F('age_alias')), avg_age=Avg(F('age')))
+
     def test_annotated_aggregate_over_annotated_aggregate(self):
         with self.assertRaisesMessage(FieldError, "Cannot compute Sum('id__max'): 'id__max' is an aggregate"):
             Book.objects.annotate(Max('id')).annotate(Sum('id__max'))