[2.2.x] Fixed #30542 -- Fixed crash of numerical aggregations with filter.

Filters in annotations crashed when used with numerical-type
aggregations (i.e. Avg, StdDev, and Variance). This was caused as the
source expressions no not necessarily have an output_field (such as the
filter field), which lead to an AttributeError: 'WhereNode' object has
no attribute output_field.

Thanks to Chuan-Zheng Lee for the report.

Regression in c690afb873cac8035a3cb3be7c597a5ff0e4b261 and two following
commits.

Backport of 4b6dfe16226a81fea464ac5f77942f4d6ba266e8 from master.

1 files changed, 4 insertions, 4 deletions

diff --git a/django/db/models/functions/mixins.py b/django/db/models/functions/mixins.py
index 8486ddb005..636340f015 100644
--- a/django/db/models/functions/mixins.py
+++ b/django/db/models/functions/mixins.py
@@ -42,9 +42,9 @@ class FixDurationInputMixin:
 class NumericOutputFieldMixin:
 
     def _resolve_output_field(self):
-        source_expressions = self.get_source_expressions()
-        if any(isinstance(s.output_field, DecimalField) for s in source_expressions):
+        source_fields = self.get_source_fields()
+        if any(isinstance(s, DecimalField) for s in source_fields):
             return DecimalField()
-        if any(isinstance(s.output_field, IntegerField) for s in source_expressions):
+        if any(isinstance(s, IntegerField) for s in source_fields):
             return FloatField()
-        return super()._resolve_output_field() if source_expressions else FloatField()
+        return super()._resolve_output_field() if source_fields else FloatField()