[typing-extensions] Simple implementation for IntVar (python#631)

Author: mrkmndz

src_py2/test_typing_extensions.py

@@ -8,7 +8,7 @@
 import types
 from unittest import TestCase, main, skipUnless
 
-from typing_extensions import NoReturn, ClassVar, Final, Literal, TypedDict
+from typing_extensions import NoReturn, ClassVar, Final, IntVar, Literal, TypedDict
 from typing_extensions import ContextManager, Counter, Deque, DefaultDict
 from typing_extensions import NewType, overload, Protocol, runtime
 import typing
@@ -158,6 +158,19 @@ def test_no_isinstance(self):
             issubclass(int, Final)
 
 
+class IntVarTests(BaseTestCase):
+    def test_valid(self):
+        T_ints = IntVar("T_ints")
+
+    def test_invalid(self):
+        with self.assertRaises(TypeError):
+            T_ints = IntVar("T_ints", int)
+        with self.assertRaises(TypeError):
+            T_ints = IntVar("T_ints", bound=int)
+        with self.assertRaises(TypeError):
+            T_ints = IntVar("T_ints", covariant=True)
+
+
 class LiteralTests(BaseTestCase):
     def test_basics(self):
         Literal[1]

src_py2/typing_extensions.py

@@ -27,6 +27,7 @@
 
     # One-off things.
     'final',
+    'IntVar',
     'Literal',
     'NewType',
     'overload',
@@ -197,6 +198,10 @@ class Other(Leaf):  # Error reported by type checker
     return f
 
 
+def IntVar(name):
+    return TypeVar(name)
+
+
 class _LiteralMeta(TypingMeta):
     """Metaclass for _Literal"""
 

src_py3/test_typing_extensions.py

@@ -13,7 +13,7 @@
 from typing import Generic
 from typing import get_type_hints
 from typing import no_type_check
-from typing_extensions import NoReturn, ClassVar, Final, Literal, Type, NewType, TypedDict
+from typing_extensions import NoReturn, ClassVar, Final, IntVar, Literal, Type, NewType, TypedDict
 try:
     from typing_extensions import Protocol, runtime
 except ImportError:
@@ -214,6 +214,20 @@ def test_no_isinstance(self):
         with self.assertRaises(TypeError):
             issubclass(int, Final)
 
+
+class IntVarTests(BaseTestCase):
+    def test_valid(self):
+        T_ints = IntVar("T_ints")
+
+    def test_invalid(self):
+        with self.assertRaises(TypeError):
+            T_ints = IntVar("T_ints", int)
+        with self.assertRaises(TypeError):
+            T_ints = IntVar("T_ints", bound=int)
+        with self.assertRaises(TypeError):
+            T_ints = IntVar("T_ints", covariant=True)
+
+
 class LiteralTests(BaseTestCase):
     def test_basics(self):
         Literal[1]

src_py3/typing_extensions.py

@@ -127,6 +127,7 @@ def _check_methods_in_mro(C, *methods):
 
     # One-off things.
     'final',
+    'IntVar',
     'Literal',
     'NewType',
     'overload',
@@ -513,6 +514,10 @@ class Other(Leaf):  # Error reported by type checker
     return f
 
 
+def IntVar(name):
+    return TypeVar(name)
+
+
 if hasattr(typing, 'Literal'):
     Literal = typing.Literal 
 elif sys.version_info[:2] >= (3, 7):