bpo-28556: Routine updates to typing (#1366)

- Add NoReturn type
- Use WrapperDescriptorType (original PR by Jim Fasarakis-Hilliard)
- Minor bug-fixes

Lib/test/test_typing.py

@@ -6,7 +6,7 @@ import sys
 from unittest import TestCase, main, skipUnless, SkipTest
 from copy import copy, deepcopy
 
-from typing import Any
+from typing import Any, NoReturn
 from typing import TypeVar, AnyStr
 from typing import T, KT, VT  # Not in __all__.
 from typing import Union, Optional
@@ -102,10 +102,6 @@ class AnyTests(BaseTestCase):
         with self.assertRaises(TypeError):
             type(Any)()
 
-    def test_cannot_subscript(self):
-        with self.assertRaises(TypeError):
-            Any[int]
-
     def test_any_works_with_alias(self):
         # These expressions must simply not fail.
         typing.Match[Any]
@@ -113,6 +109,40 @@ class AnyTests(BaseTestCase):
         typing.IO[Any]
 
 
+class NoReturnTests(BaseTestCase):
+
+    def test_noreturn_instance_type_error(self):
+        with self.assertRaises(TypeError):
+            isinstance(42, NoReturn)
+
+    def test_noreturn_subclass_type_error(self):
+        with self.assertRaises(TypeError):
+            issubclass(Employee, NoReturn)
+        with self.assertRaises(TypeError):
+            issubclass(NoReturn, Employee)
+
+    def test_repr(self):
+        self.assertEqual(repr(NoReturn), 'typing.NoReturn')
+
+    def test_not_generic(self):
+        with self.assertRaises(TypeError):
+            NoReturn[int]
+
+    def test_cannot_subclass(self):
+        with self.assertRaises(TypeError):
+            class A(NoReturn):
+                pass
+        with self.assertRaises(TypeError):
+            class A(type(NoReturn)):
+                pass
+
+    def test_cannot_instantiate(self):
+        with self.assertRaises(TypeError):
+            NoReturn()
+        with self.assertRaises(TypeError):
+            type(NoReturn)()
+
+
 class TypeVarTests(BaseTestCase):
 
     def test_basic_plain(self):
@@ -2273,6 +2303,14 @@ class XMethBad(NamedTuple):
         return 'no chance for this'
 """)
 
+        with self.assertRaises(AttributeError):
+            exec("""
+class XMethBad2(NamedTuple):
+    x: int
+    def _source(self):
+        return 'no chance for this as well'
+""")
+
     @skipUnless(PY36, 'Python 3.6 required')
     def test_namedtuple_keyword_usage(self):
         LocalEmployee = NamedTuple("LocalEmployee", name=str, age=int)
@@ -2420,6 +2458,9 @@ class AllTests(BaseTestCase):
         self.assertNotIn('sys', a)
         # Check that Text is defined.
         self.assertIn('Text', a)
+        # Check previously missing classes.
+        self.assertIn('SupportsBytes', a)
+        self.assertIn('SupportsComplex', a)
 
 
 if __name__ == '__main__':