Have Protocol inherit from typing.Generic on 3.8+ (#184)

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 - Change deprecated `@runtime` to formal API `@runtime_checkable` in the error
   message. Patch by Xuehai Pan.
+- Fix regression in 4.6.0 where attempting to define a `Protocol` that was
+  generic over a `ParamSpec` or a `TypeVarTuple` would cause `TypeError` to be
+  raised. Patch by Alex Waygood.
 
 # Release 4.6.0 (May 22, 2023)
 

src/test_typing_extensions.py

@@ -2613,6 +2613,62 @@ class CustomProtocolWithoutInitB(Protocol):
 
         self.assertEqual(CustomProtocolWithoutInitA.__init__, CustomProtocolWithoutInitB.__init__)
 
+    def test_protocol_generic_over_paramspec(self):
+        P = ParamSpec("P")
+        T = TypeVar("T")
+        T2 = TypeVar("T2")
+
+        class MemoizedFunc(Protocol[P, T, T2]):
+            cache: typing.Dict[T2, T]
+            def __call__(self, *args: P.args, **kwargs: P.kwargs) -> T: ...
+
+        self.assertEqual(MemoizedFunc.__parameters__, (P, T, T2))
+        self.assertTrue(MemoizedFunc._is_protocol)
+
+        with self.assertRaises(TypeError):
+            MemoizedFunc[[int, str, str]]
+
+        if sys.version_info >= (3, 10):
+            # These unfortunately don't pass on <=3.9,
+            # due to typing._type_check on older Python versions
+            X = MemoizedFunc[[int, str, str], T, T2]
+            self.assertEqual(X.__parameters__, (T, T2))
+            self.assertEqual(X.__args__, ((int, str, str), T, T2))
+
+            Y = X[bytes, memoryview]
+            self.assertEqual(Y.__parameters__, ())
+            self.assertEqual(Y.__args__, ((int, str, str), bytes, memoryview))
+
+    def test_protocol_generic_over_typevartuple(self):
+        Ts = TypeVarTuple("Ts")
+        T = TypeVar("T")
+        T2 = TypeVar("T2")
+
+        class MemoizedFunc(Protocol[Unpack[Ts], T, T2]):
+            cache: typing.Dict[T2, T]
+            def __call__(self, *args: Unpack[Ts]) -> T: ...
+
+        self.assertEqual(MemoizedFunc.__parameters__, (Ts, T, T2))
+        self.assertTrue(MemoizedFunc._is_protocol)
+
+        things = "arguments" if sys.version_info >= (3, 11) else "parameters"
+
+        # A bug was fixed in 3.11.1
+        # (https://github.com/python/cpython/commit/74920aa27d0c57443dd7f704d6272cca9c507ab3)
+        # That means this assertion doesn't pass on 3.11.0,
+        # but it passes on all other Python versions
+        if sys.version_info[:3] != (3, 11, 0):
+            with self.assertRaisesRegex(TypeError, f"Too few {things}"):
+                MemoizedFunc[int]
+
+        X = MemoizedFunc[int, T, T2]
+        self.assertEqual(X.__parameters__, (T, T2))
+        self.assertEqual(X.__args__, (int, T, T2))
+
+        Y = X[bytes, memoryview]
+        self.assertEqual(Y.__parameters__, ())
+        self.assertEqual(Y.__args__, (int, bytes, memoryview))
+
 
 class Point2DGeneric(Generic[T], TypedDict):
     a: T
@@ -3402,13 +3458,18 @@ def test_user_generics(self):
         class X(Generic[T, P]):
             pass
 
-        G1 = X[int, P_2]
-        self.assertEqual(G1.__args__, (int, P_2))
-        self.assertEqual(G1.__parameters__, (P_2,))
+        class Y(Protocol[T, P]):
+            pass
+
+        for klass in X, Y:
+            with self.subTest(klass=klass.__name__):
+                G1 = klass[int, P_2]
+                self.assertEqual(G1.__args__, (int, P_2))
+                self.assertEqual(G1.__parameters__, (P_2,))
 
-        G2 = X[int, Concatenate[int, P_2]]
-        self.assertEqual(G2.__args__, (int, Concatenate[int, P_2]))
-        self.assertEqual(G2.__parameters__, (P_2,))
+                G2 = klass[int, Concatenate[int, P_2]]
+                self.assertEqual(G2.__args__, (int, Concatenate[int, P_2]))
+                self.assertEqual(G2.__parameters__, (P_2,))
 
         # The following are some valid uses cases in PEP 612 that don't work:
         # These do not work in 3.9, _type_check blocks the list and ellipsis.
@@ -3421,6 +3482,9 @@ class X(Generic[T, P]):
         class Z(Generic[P]):
             pass
 
+        class ProtoZ(Protocol[P]):
+            pass
+
     def test_pickle(self):
         global P, P_co, P_contra, P_default
         P = ParamSpec('P')
@@ -3727,31 +3791,49 @@ def test_concatenation(self):
         self.assertEqual(Tuple[int, Unpack[Xs], str].__args__,
                          (int, Unpack[Xs], str))
         class C(Generic[Unpack[Xs]]): pass
-        self.assertEqual(C[int, Unpack[Xs]].__args__, (int, Unpack[Xs]))
-        self.assertEqual(C[Unpack[Xs], int].__args__, (Unpack[Xs], int))
-        self.assertEqual(C[int, Unpack[Xs], str].__args__,
-                         (int, Unpack[Xs], str))
+        class D(Protocol[Unpack[Xs]]): pass
+        for klass in C, D:
+            with self.subTest(klass=klass.__name__):
+                self.assertEqual(klass[int, Unpack[Xs]].__args__, (int, Unpack[Xs]))
+                self.assertEqual(klass[Unpack[Xs], int].__args__, (Unpack[Xs], int))
+                self.assertEqual(klass[int, Unpack[Xs], str].__args__,
+                                 (int, Unpack[Xs], str))
 
     def test_class(self):
         Ts = TypeVarTuple('Ts')
 
         class C(Generic[Unpack[Ts]]): pass
-        self.assertEqual(C[int].__args__, (int,))
-        self.assertEqual(C[int, str].__args__, (int, str))
+        class D(Protocol[Unpack[Ts]]): pass
+
+        for klass in C, D:
+            with self.subTest(klass=klass.__name__):
+                self.assertEqual(klass[int].__args__, (int,))
+                self.assertEqual(klass[int, str].__args__, (int, str))
 
         with self.assertRaises(TypeError):
             class C(Generic[Unpack[Ts], int]): pass
 
+        with self.assertRaises(TypeError):
+            class D(Protocol[Unpack[Ts], int]): pass
+
         T1 = TypeVar('T')
         T2 = TypeVar('T')
         class C(Generic[T1, T2, Unpack[Ts]]): pass
-        self.assertEqual(C[int, str].__args__, (int, str))
-        self.assertEqual(C[int, str, float].__args__, (int, str, float))
-        self.assertEqual(C[int, str, float, bool].__args__, (int, str, float, bool))
-        # TODO This should probably also fail on 3.11, pending changes to CPython.
-        if not TYPING_3_11_0:
-            with self.assertRaises(TypeError):
-                C[int]
+        class D(Protocol[T1, T2, Unpack[Ts]]): pass
+        for klass in C, D:
+            with self.subTest(klass=klass.__name__):
+                self.assertEqual(klass[int, str].__args__, (int, str))
+                self.assertEqual(klass[int, str, float].__args__, (int, str, float))
+                self.assertEqual(
+                    klass[int, str, float, bool].__args__, (int, str, float, bool)
+                )
+                # A bug was fixed in 3.11.1
+                # (https://github.com/python/cpython/commit/74920aa27d0c57443dd7f704d6272cca9c507ab3)
+                # That means this assertion doesn't pass on 3.11.0,
+                # but it passes on all other Python versions
+                if sys.version_info[:3] != (3, 11, 0):
+                    with self.assertRaises(TypeError):
+                        klass[int]
 
 
 class TypeVarTupleTests(BaseTestCase):