test and correct _is_param_expr for typing.Concatenate

Author: Daraan

src/test_typing_extensions.py

@@ -5326,6 +5326,16 @@ class ProtoZ(Protocol[P]):
                 G10args = G10.__args__[0] if sys.version_info >= (3, 10) else G10.__args__
                 self.assertEqual(G10args, (int, Concatenate[str, P], ))
 
+    @skipUnless(TYPING_3_10_0, "ParamSpec not present before 3.10")
+    def test_is_param_expr(self):
+        P = ParamSpec("P")
+        P_typing = typing.ParamSpec("P_typing")
+        self.assertTrue(typing_extensions._is_param_expr(P))
+        self.assertTrue(typing_extensions._is_param_expr(P_typing))
+        if hasattr(typing, "_is_param_expr"):
+            self.assertTrue(typing._is_param_expr(P))
+            self.assertTrue(typing._is_param_expr(P_typing))
+
     def test_single_argument_generic_with_parameter_expressions(self):
         P = ParamSpec("P")
         T = TypeVar("T")
@@ -5571,6 +5581,17 @@ def test_eq(self):
         self.assertNotEqual(C4, C6)
 
 
+    @skipUnless(TYPING_3_10_0, "Concatenate not present before 3.10")
+    def test_is_param_expr(self):
+        P = ParamSpec('P')
+        concat = Concatenate[str, P]
+        typing_concat = typing.Concatenate[str, P]
+        self.assertTrue(typing_extensions._is_param_expr(concat))
+        self.assertTrue(typing_extensions._is_param_expr(typing_concat))
+        if hasattr(typing, "_is_param_expr"):
+            self.assertTrue(typing._is_param_expr(concat))
+            self.assertTrue(typing._is_param_expr(typing_concat))
+
 class TypeGuardTests(BaseTestCase):
     def test_basics(self):
         TypeGuard[int]  # OK

src/typing_extensions.py

@@ -3006,10 +3006,23 @@ def wrapper(*args, **kwargs):
                     f"a class or callable, not {arg!r}"
                 )
 
-def _is_param_expr(arg):
-    return arg is ... or isinstance(
-        arg, (tuple, list, ParamSpec, _ConcatenateGenericAlias)
-    )
+if sys.version_info < (3, 10):
+    def _is_param_expr(arg):
+        return arg is ... or isinstance(
+            arg, (tuple, list, ParamSpec, _ConcatenateGenericAlias)
+        )
+else:
+    def _is_param_expr(arg):
+        return arg is ... or isinstance(
+            arg,
+            (
+                tuple,
+                list,
+                ParamSpec,
+                _ConcatenateGenericAlias,
+                typing._ConcatenateGenericAlias,
+            ),
+        )
 
 # We have to do some monkey patching to deal with the dual nature of
 # Unpack/TypeVarTuple: