Backport fix for #192 to Python 2. Remove optimistic TODO about #196.

Author: Guido van Rossum

python2/test_typing.py

@@ -673,6 +673,9 @@ def foo(x):
             assert type(a) is Node
             assert type(b) is Node
             assert type(c) is Node
+            assert a.label == x
+            assert b.label == x
+            assert c.label == x
 
         foo(42)
 

python2/typing.py

@@ -1093,7 +1093,11 @@ def __new__(cls, *args, **kwds):
         for i, c in enumerate(cls.__mro__[:-1]):
             if isinstance(c, GenericMeta) and _gorg(c) is Generic:
                 next_in_mro = cls.__mro__[i+1]
-        return next_in_mro.__new__(_gorg(cls))
+        origin = _gorg(cls)
+        obj = next_in_mro.__new__(origin)
+        if origin is not cls:
+            obj.__init__(*args, **kwds)
+        return obj
 
 
 def cast(typ, val):

src/typing.py

@@ -1069,8 +1069,6 @@ def lookup_name(mapping: Mapping[X, Y], key: X, default: Y) -> Y:
 
     __slots__ = ()
 
-    # TODO: GenericMeta should compute next_in_mro and stuff its
-    # __new__ in the class dict, if origin is cls.  Issue #196.
     def __new__(cls, *args, **kwds):
         next_in_mro = object
         # Look for the last occurrence of Generic or Generic[...].