Add more tests for variable substitution in generics (GH-31170)

(cherry picked from commit 3da5526)

Co-authored-by: Serhiy Storchaka <[email protected]>

Author: miss-islington

Lib/test/test_typing.py

@@ -247,6 +247,15 @@ def test_no_bivariant(self):
         with self.assertRaises(ValueError):
             TypeVar('T', covariant=True, contravariant=True)
 
+    def test_bad_var_substitution(self):
+        T = TypeVar('T')
+        for arg in (), (int, str):
+            with self.subTest(arg=arg):
+                with self.assertRaises(TypeError):
+                    List[T][arg]
+                with self.assertRaises(TypeError):
+                    list[T][arg]
+
 
 class UnionTests(BaseTestCase):
 
@@ -560,8 +569,11 @@ def test_var_substitution(self):
         C2 = Callable[[KT, T], VT]
         C3 = Callable[..., T]
         self.assertEqual(C1[str], Callable[[int, str], str])
+        if Callable is typing.Callable:
+            self.assertEqual(C1[None], Callable[[int, type(None)], type(None)])
         self.assertEqual(C2[int, float, str], Callable[[int, float], str])
         self.assertEqual(C3[int], Callable[..., int])
+        self.assertEqual(C3[NoReturn], Callable[..., NoReturn])
 
         # multi chaining
         C4 = C2[int, VT, str]
@@ -4880,6 +4892,17 @@ class X(Generic[P, P2]):
         self.assertEqual(G1.__args__, ((int, str), (bytes,)))
         self.assertEqual(G2.__args__, ((int,), (str, bytes)))
 
+    def test_bad_var_substitution(self):
+        T = TypeVar('T')
+        P = ParamSpec('P')
+        bad_args = (42, int, None, T, int|str, Union[int, str])
+        for arg in bad_args:
+            with self.subTest(arg=arg):
+                with self.assertRaises(TypeError):
+                    typing.Callable[P, T][arg, str]
+                with self.assertRaises(TypeError):
+                    collections.abc.Callable[P, T][arg, str]
+
     def test_no_paramspec_in__parameters__(self):
         # ParamSpec should not be found in __parameters__
         # of generics. Usages outside Callable, Concatenate
@@ -4909,6 +4932,10 @@ def test_paramspec_in_nested_generics(self):
         self.assertEqual(G1.__parameters__, (P, T))
         self.assertEqual(G2.__parameters__, (P, T))
         self.assertEqual(G3.__parameters__, (P, T))
+        C = Callable[[int, str], float]
+        self.assertEqual(G1[[int, str], float], List[C])
+        self.assertEqual(G2[[int, str], float], list[C])
+        self.assertEqual(G3[[int, str], float], list[C] | int)
 
 
 class ConcatenateTests(BaseTestCase):