bpo-28556: Minor updates to typing module (#3550)

* Copy changes to typing from upstream repo
* Add NEWS entry

1 files changed, 29 insertions, 50 deletions

diff --git a/Lib/typing.py b/Lib/typing.py
index c487afc..609f813 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -376,7 +376,7 @@ def _type_check(arg, msg):
     if (
         type(arg).__name__ in ('_Union', '_Optional') and
         not getattr(arg, '__origin__', None) or
-        isinstance(arg, TypingMeta) and _gorg(arg) in (Generic, _Protocol)
+        isinstance(arg, TypingMeta) and arg._gorg in (Generic, _Protocol)
     ):
         raise TypeError("Plain %s is not valid as type argument" % arg)
     return arg
@@ -849,29 +849,6 @@ class _Optional(_FinalTypingBase, _root=True):
 Optional = _Optional(_root=True)
 
 
-def _gorg(a):
-    """Return the farthest origin of a generic class (internal helper)."""
-    assert isinstance(a, GenericMeta)
-    while a.__origin__ is not None:
-        a = a.__origin__
-    return a
-
-
-def _geqv(a, b):
-    """Return whether two generic classes are equivalent (internal helper).
-
-    The intention is to consider generic class X and any of its
-    parameterized forms (X[T], X[int], etc.) as equivalent.
-
-    However, X is not equivalent to a subclass of X.
-
-    The relation is reflexive, symmetric and transitive.
-    """
-    assert isinstance(a, GenericMeta) and isinstance(b, GenericMeta)
-    # Reduce each to its origin.
-    return _gorg(a) is _gorg(b)
-
-
 def _next_in_mro(cls):
     """Helper for Generic.__new__.
 
@@ -881,7 +858,7 @@ def _next_in_mro(cls):
     next_in_mro = object
     # Look for the last occurrence of Generic or Generic[...].
     for i, c in enumerate(cls.__mro__[:-1]):
-        if isinstance(c, GenericMeta) and _gorg(c) is Generic:
+        if isinstance(c, GenericMeta) and c._gorg is Generic:
             next_in_mro = cls.__mro__[i + 1]
     return next_in_mro
 
@@ -991,14 +968,15 @@ class GenericMeta(TypingMeta, abc.ABCMeta):
         initial_bases = bases
         if extra is not None and type(extra) is abc.ABCMeta and extra not in bases:
             bases = (extra,) + bases
-        bases = tuple(_gorg(b) if isinstance(b, GenericMeta) else b for b in bases)
+        bases = tuple(b._gorg if isinstance(b, GenericMeta) else b for b in bases)
 
         # remove bare Generic from bases if there are other generic bases
         if any(isinstance(b, GenericMeta) and b is not Generic for b in bases):
             bases = tuple(b for b in bases if b is not Generic)
         namespace.update({'__origin__': origin, '__extra__': extra})
         self = super().__new__(cls, name, bases, namespace, _root=True)
-
+        super(GenericMeta, self).__setattr__('_gorg',
+                                             self if not origin else origin._gorg)
         self.__parameters__ = tvars
         # Be prepared that GenericMeta will be subclassed by TupleMeta
         # and CallableMeta, those two allow ..., (), or [] in __args___.
@@ -1041,7 +1019,7 @@ class GenericMeta(TypingMeta, abc.ABCMeta):
     def _abc_negative_cache(self):
         if isinstance(self.__extra__, abc.ABCMeta):
             return self.__extra__._abc_negative_cache
-        return _gorg(self)._abc_generic_negative_cache
+        return self._gorg._abc_generic_negative_cache
 
     @_abc_negative_cache.setter
     def _abc_negative_cache(self, value):
@@ -1055,7 +1033,7 @@ class GenericMeta(TypingMeta, abc.ABCMeta):
     def _abc_negative_cache_version(self):
         if isinstance(self.__extra__, abc.ABCMeta):
             return self.__extra__._abc_negative_cache_version
-        return _gorg(self)._abc_generic_negative_cache_version
+        return self._gorg._abc_generic_negative_cache_version
 
     @_abc_negative_cache_version.setter
     def _abc_negative_cache_version(self, value):
@@ -1105,7 +1083,7 @@ class GenericMeta(TypingMeta, abc.ABCMeta):
         if self.__origin__ is None:
             return self
         tree_args = _subs_tree(self, tvars, args)
-        return (_gorg(self),) + tuple(tree_args)
+        return (self._gorg,) + tuple(tree_args)
 
     def __eq__(self, other):
         if not isinstance(other, GenericMeta):
@@ -1121,7 +1099,7 @@ class GenericMeta(TypingMeta, abc.ABCMeta):
     def __getitem__(self, params):
         if not isinstance(params, tuple):
             params = (params,)
-        if not params and not _gorg(self) is Tuple:
+        if not params and self._gorg is not Tuple:
             raise TypeError(
                 "Parameter list to %s[...] cannot be empty" % _qualname(self))
         msg = "Parameters to generic types must be types."
@@ -1189,14 +1167,14 @@ class GenericMeta(TypingMeta, abc.ABCMeta):
                               self.__extra__, self.__orig_bases__)
 
     def __setattr__(self, attr, value):
-        # We consider all the subscripted genrics as proxies for original class
+        # We consider all the subscripted generics as proxies for original class
         if (
             attr.startswith('__') and attr.endswith('__') or
             attr.startswith('_abc_')
         ):
             super(GenericMeta, self).__setattr__(attr, value)
         else:
-            super(GenericMeta, _gorg(self)).__setattr__(attr, value)
+            super(GenericMeta, self._gorg).__setattr__(attr, value)
 
 
 # Prevent checks for Generic to crash when defining Generic.
@@ -1209,7 +1187,7 @@ def _generic_new(base_cls, cls, *args, **kwds):
     if cls.__origin__ is None:
         return base_cls.__new__(cls)
     else:
-        origin = _gorg(cls)
+        origin = cls._gorg
         obj = base_cls.__new__(origin)
         try:
             obj.__orig_class__ = cls
@@ -1243,7 +1221,7 @@ class Generic(metaclass=GenericMeta):
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, Generic):
+        if cls._gorg is Generic:
             raise TypeError("Type Generic cannot be instantiated; "
                             "it can be used only as a base class")
         return _generic_new(cls.__next_in_mro__, cls, *args, **kwds)
@@ -1265,7 +1243,7 @@ class TupleMeta(GenericMeta):
 
     @_tp_cache
     def __getitem__(self, parameters):
-        if self.__origin__ is not None or not _geqv(self, Tuple):
+        if self.__origin__ is not None or self._gorg is not Tuple:
             # Normal generic rules apply if this is not the first subscription
             # or a subscription of a subclass.
             return super().__getitem__(parameters)
@@ -1307,7 +1285,7 @@ class Tuple(tuple, extra=tuple, metaclass=TupleMeta):
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, Tuple):
+        if cls._gorg is Tuple:
             raise TypeError("Type Tuple cannot be instantiated; "
                             "use tuple() instead")
         return _generic_new(tuple, cls, *args, **kwds)
@@ -1322,7 +1300,7 @@ class CallableMeta(GenericMeta):
         return self._tree_repr(self._subs_tree())
 
     def _tree_repr(self, tree):
-        if _gorg(self) is not Callable:
+        if self._gorg is not Callable:
             return super()._tree_repr(tree)
         # For actual Callable (not its subclass) we override
         # super()._tree_repr() for nice formatting.
@@ -1342,7 +1320,7 @@ class CallableMeta(GenericMeta):
         with hashable arguments to improve speed.
         """
 
-        if self.__origin__ is not None or not _geqv(self, Callable):
+        if self.__origin__ is not None or self._gorg is not Callable:
             return super().__getitem__(parameters)
         if not isinstance(parameters, tuple) or len(parameters) != 2:
             raise TypeError("Callable must be used as "
@@ -1384,7 +1362,7 @@ class Callable(extra=collections_abc.Callable, metaclass=CallableMeta):
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, Callable):
+        if cls._gorg is Callable:
             raise TypeError("Type Callable cannot be instantiated; "
                             "use a non-abstract subclass instead")
         return _generic_new(cls.__next_in_mro__, cls, *args, **kwds)
@@ -1568,7 +1546,7 @@ def no_type_check(arg):
     if isinstance(arg, type):
         arg_attrs = arg.__dict__.copy()
         for attr, val in arg.__dict__.items():
-            if val in arg.__bases__:
+            if val in arg.__bases__ + (arg,):
                 arg_attrs.pop(attr)
         for obj in arg_attrs.values():
             if isinstance(obj, types.FunctionType):
@@ -1687,6 +1665,7 @@ class _ProtocolMeta(GenericMeta):
                             attr != '__annotations__' and
                             attr != '__weakref__' and
                             attr != '_is_protocol' and
+                            attr != '_gorg' and
                             attr != '__dict__' and
                             attr != '__args__' and
                             attr != '__slots__' and
@@ -1892,7 +1871,7 @@ class List(list, MutableSequence[T], extra=list):
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, List):
+        if cls._gorg is List:
             raise TypeError("Type List cannot be instantiated; "
                             "use list() instead")
         return _generic_new(list, cls, *args, **kwds)
@@ -1903,7 +1882,7 @@ class Deque(collections.deque, MutableSequence[T], extra=collections.deque):
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, Deque):
+        if cls._gorg is Deque:
             return collections.deque(*args, **kwds)
         return _generic_new(collections.deque, cls, *args, **kwds)
 
@@ -1913,7 +1892,7 @@ class Set(set, MutableSet[T], extra=set):
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, Set):
+        if cls._gorg is Set:
             raise TypeError("Type Set cannot be instantiated; "
                             "use set() instead")
         return _generic_new(set, cls, *args, **kwds)
@@ -1923,7 +1902,7 @@ class FrozenSet(frozenset, AbstractSet[T_co], extra=frozenset):
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, FrozenSet):
+        if cls._gorg is FrozenSet:
             raise TypeError("Type FrozenSet cannot be instantiated; "
                             "use frozenset() instead")
         return _generic_new(frozenset, cls, *args, **kwds)
@@ -2014,7 +1993,7 @@ class Dict(dict, MutableMapping[KT, VT], extra=dict):
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, Dict):
+        if cls._gorg is Dict:
             raise TypeError("Type Dict cannot be instantiated; "
                             "use dict() instead")
         return _generic_new(dict, cls, *args, **kwds)
@@ -2026,7 +2005,7 @@ class DefaultDict(collections.defaultdict, MutableMapping[KT, VT],
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, DefaultDict):
+        if cls._gorg is DefaultDict:
             return collections.defaultdict(*args, **kwds)
         return _generic_new(collections.defaultdict, cls, *args, **kwds)
 
@@ -2036,7 +2015,7 @@ class Counter(collections.Counter, Dict[T, int], extra=collections.Counter):
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, Counter):
+        if cls._gorg is Counter:
             return collections.Counter(*args, **kwds)
         return _generic_new(collections.Counter, cls, *args, **kwds)
 
@@ -2051,7 +2030,7 @@ if hasattr(collections, 'ChainMap'):
         __slots__ = ()
 
         def __new__(cls, *args, **kwds):
-            if _geqv(cls, ChainMap):
+            if cls._gorg is ChainMap:
                 return collections.ChainMap(*args, **kwds)
             return _generic_new(collections.ChainMap, cls, *args, **kwds)
 
@@ -2070,7 +2049,7 @@ class Generator(Iterator[T_co], Generic[T_co, T_contra, V_co],
     __slots__ = ()
 
     def __new__(cls, *args, **kwds):
-        if _geqv(cls, Generator):
+        if cls._gorg is Generator:
             raise TypeError("Type Generator cannot be instantiated; "
                             "create a subclass instead")
         return _generic_new(_G_base, cls, *args, **kwds)