Allow simple assignments to None in enum class scopes (#479)

Author: AlexWaygood

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Change Log
 
+## Unreleased
+
+Bugfixes:
+* Fix Y026 false positive: allow simple assignment to `None` in class scopes
+  if the class is known to be an enum class.
+
 ## 24.3.1
 
 New error codes:

pyi.py

@@ -1219,7 +1219,7 @@ def _check_for_type_aliases(
             isinstance(assignment, ast.Subscript)
             or _is_valid_pep_604_union(assignment)
             or _is_Any(assignment)
-            or _is_None(assignment)
+            or (_is_None(assignment) and not self.visiting_enum_class)
         ):
             new_node = ast.AnnAssign(
                 target=target,

tests/aliases.pyi

@@ -2,6 +2,7 @@
 import array
 import builtins
 import collections.abc
+import enum
 import typing
 from collections.abc import Mapping
 from typing import (
@@ -86,3 +87,6 @@ _snake_case_alias2: TypeAlias = Literal["whatever"]  # Y042 Type aliases should
 
 # check that this edge case doesn't crash the plugin
 _: TypeAlias = str | int
+
+class FooEnum(enum.Enum):
+    BAR = None  # shouldn't emit Y026 because it's an assignment in an enum class