Add _generate_next_value_ to StrEnum (#10390)

Fixes https://github.com/python/typeshed/issues/10384

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

stdlib/enum.pyi

@@ -237,6 +237,8 @@ if sys.version_info >= (3, 11):
         _value_: str
         @_magic_enum_attr
         def value(self) -> str: ...
+        @staticmethod
+        def _generate_next_value_(name: str, start: int, count: int, last_values: list[str]) -> str: ...
 
     class EnumCheck(StrEnum):
         CONTINUOUS: str

test_cases/stdlib/check_enum.py

@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+import enum
+import sys
+from typing_extensions import Literal, assert_type
+
+if sys.version_info >= (3, 11):
+
+    class Foo(enum.StrEnum):
+        X = enum.auto()
+
+    assert_type(Foo.X, Literal[Foo.X])
+    assert_type(Foo.X.value, str)

tests/stubtest_allowlists/py311.txt

@@ -17,6 +17,8 @@ configparser.LegacyInterpolation.__init__
 configparser.ParsingError.filename
 enum.Enum.__init__
 enum.Enum._generate_next_value_
+# Not strictly speaking a staticmethod on 3.11, but it acts like one:
+enum.StrEnum._generate_next_value_
 importlib.abc.Finder.find_module
 ipaddress._BaseNetwork.broadcast_address
 ipaddress._BaseNetwork.hostmask