Type should not inherit from type. (#267)

Fixes #266.

python2/test_typing.py

@@ -1159,6 +1159,19 @@ def new_user(user_class):
 
         joe = new_user(BasicUser)
 
+    def test_type_optional(self):
+        A = Optional[Type[BaseException]]
+
+        def foo(a):
+            # type: (A) -> Optional[BaseException]
+            if a is None:
+                return None
+            else:
+                return a()
+
+        assert isinstance(foo(KeyboardInterrupt), KeyboardInterrupt)
+        assert foo(None) is None
+
 
 class NewTypeTests(BaseTestCase):
 

python2/typing.py

@@ -1529,7 +1529,7 @@ def __new__(cls, *args, **kwds):
 
 
 # This is not a real generic class.  Don't use outside annotations.
-class Type(type, Generic[CT_co]):
+class Type(Generic[CT_co]):
     """A special construct usable to annotate class objects.
 
     For example, suppose we have the following classes::

src/test_typing.py

@@ -1426,6 +1426,18 @@ def new_user(user_class: Type[U]) -> U:
 
         joe = new_user(BasicUser)
 
+    def test_type_optional(self):
+        A = Optional[Type[BaseException]]
+
+        def foo(a: A) -> Optional[BaseException]:
+            if a is None:
+                return None
+            else:
+                return a()
+
+        assert isinstance(foo(KeyboardInterrupt), KeyboardInterrupt)
+        assert foo(None) is None
+
 
 class NewTypeTests(BaseTestCase):
 

src/typing.py

@@ -1605,7 +1605,7 @@ def __new__(cls, *args, **kwds):
 
 
 # This is not a real generic class.  Don't use outside annotations.
-class Type(type, Generic[CT_co], extra=type):
+class Type(Generic[CT_co], extra=type):
     """A special construct usable to annotate class objects.
 
     For example, suppose we have the following classes::