pythongh-119972: typing: Fix specialization of generic with broken __…

…eq__

Lib/test/test_typing.py

@@ -4866,6 +4866,18 @@ class B(Generic[T]):
         self.assertEqual(A[T], A[T])
         self.assertNotEqual(A[T], B[T])
 
+    def test_buggy_eq(self):
+        class BrokenEq(abc.ABCMeta):
+            def __eq__(self, other):
+                raise TypeError("I'm broken")
+
+        class G(Generic[T], metaclass=BrokenEq):
+            pass
+
+        alias = G[int]
+        self.assertIs(get_origin(alias), G)
+        self.assertEqual(get_args(alias), (int,))
+
     def test_multiple_inheritance(self):
 
         class A(Generic[T, VT]):

Lib/typing.py

@@ -1077,7 +1077,7 @@ def _generic_class_getitem(cls, params):
         params = (params,)
 
     params = tuple(_type_convert(p) for p in params)
-    is_generic_or_protocol = cls in (Generic, Protocol)
+    is_generic_or_protocol = cls is Generic or cls is Protocol
 
     if is_generic_or_protocol:
         # Generic and Protocol can only be subscripted with unique type variables.

Misc/NEWS.d/next/Library/2024-06-03-04-14-14.gh-issue-119972.nwtxx6.rst

@@ -0,0 +1,2 @@
+Fix specialization of :class:`typing.Generic` class with a broken ``__eq__``
+method. Patch by Jelle Zijlstra.