Backport python/cpython#31628

[Gobot1234]

Needs decision on how to fix failing test

Fixes#104

[JelleZijlstra]

cc @adriangb if you're interested.

[JelleZijlstra]

Looking at some of the failing tests:

• 3.7 is totally broken because of the inheritance from typing.Generic. This needs to be fixed. We probably need to preserve the existing 3.7 implementation.
• 3.10 fails on class X(Generic[T], Protocol):. If Protocol[T] works we can live without that, but would be nice to support both ways.
• 3.10 allows class P(Protocol[T, T]): pass. Not the end of the world but a little odd.

[AlexWaygood]

@Gobot1234, following recent changes I've made to typing_extensions.Protocol over the last few days, I think you can get away with a much simpler patch now. This patch passes all tests locally for me, on Python 3.11 and Python 3.7 (the diff is against main, not against this PR branch):

diff --git a/src/test_typing_extensions.py b/src/test_typing_extensions.py
index 3a483b5..6fcfafb 100644
--- a/src/test_typing_extensions.py+++ b/src/test_typing_extensions.py@@ -1454,6 +1454,32 @@ class ProtocolTests(BaseTestCase):
class CG(PG[T]): pass
self.assertIsInstance(CG[int](), CG)
+ def test_protocol_defining_init_does_not_get_overridden(self):+ # check that P.__init__ doesn't get clobbered+ # see https://bugs.python.org/issue44807++ class P(Protocol):+ x: int+ def __init__(self, x: int) -> None:+ self.x = x+ class C: pass++ c = C()+ P.__init__(c, 1)+ self.assertEqual(c.x, 1)++ def test_concrete_class_inheriting_init_from_protocol(self):+ class P(Protocol):+ x: int+ def __init__(self, x: int) -> None:+ self.x = x++ class C(P): pass++ c = C(1)+ self.assertIsInstance(c, C)+ self.assertEqual(c.x, 1)+
def test_cannot_instantiate_abstract(self):
@runtime_checkable
class P(Protocol):
diff --git a/src/typing_extensions.py b/src/typing_extensions.py
index c28680c..94218ac 100644
--- a/src/typing_extensions.py+++ b/src/typing_extensions.py@@ -662,7 +662,8 @@ else:
isinstance(base, _ProtocolMeta) and base._is_protocol):
raise TypeError('Protocols can only inherit from other'
f' protocols, got {repr(base)}')
- cls.__init__ = _no_init+ if cls.__init__ is Protocol.__init__:+ cls.__init__ = _no_init

[Gobot1234]

I may have forgotten about this PR 😅. That does look a lot nicer though.

[AlexWaygood]

I may have forgotten about this PR 😅. That does look a lot nicer though.

Happy to take over if you like, or leave it to you -- whatever you prefer :)

[Gobot1234]

If you already have it working that'd be great, thank you