[3.11] gh-103479: [Enum] require __new__ to be considered a data type (GH-103495) (GH-103514)

a mixin must either have a __new__ method, or be a dataclass, to be interpreted as a data-type; an __init__ method is not enough (restores pre-3.11 behavior for non-dataclasses).

(cherry picked from commit a6f95941a3d686707fb38e0f37758e666f25e180)
Co-authored-by: Ethan Furman <ethan@stoneleaf.us>

1 files changed, 6 insertions, 5 deletions

diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index d3b4832..188e1a1 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -2672,19 +2672,18 @@ class TestSpecial(unittest.TestCase):
         self.assertTrue(Entries.ENTRY1.value == Foo(1), Entries.ENTRY1.value)
         self.assertEqual(repr(Entries.ENTRY1), '<Entries.ENTRY1: Foo(a=1)>')
 
-    def test_repr_with_init_data_type_mixin(self):
-        # non-data_type is a mixin that doesn't define __new__
+    def test_repr_with_init_mixin(self):
         class Foo:
             def __init__(self, a):
                 self.a = a
             def __repr__(self):
-                return f'Foo(a={self.a!r})'
+                return 'Foo(a=%r)' % self._value_
         class Entries(Foo, Enum):
             ENTRY1 = 1
         #
-        self.assertEqual(repr(Entries.ENTRY1), '<Entries.ENTRY1: Foo(a=1)>')
+        self.assertEqual(repr(Entries.ENTRY1), 'Foo(a=1)')
 
-    def test_repr_and_str_with_non_data_type_mixin(self):
+    def test_repr_and_str_with_no_init_mixin(self):
         # non-data_type is a mixin that doesn't define __new__
         class Foo:
             def __repr__(self):
@@ -2796,6 +2795,8 @@ class TestSpecial(unittest.TestCase):
 
     def test_init_exception(self):
         class Base:
+            def __new__(cls, *args):
+                return object.__new__(cls)
             def __init__(self, x):
                 raise ValueError("I don't like", x)
         with self.assertRaises(TypeError):