Issue #28556: merge 5 more typing changes from upstream (#340, #344, #348, #349, #350)
diff --git a/Lib/typing.py b/Lib/typing.py
index 2821c3c..b798830 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -27,6 +27,8 @@
# ABCs (from collections.abc).
'AbstractSet', # collections.abc.Set.
+ 'GenericMeta', # subclass of abc.ABCMeta and a metaclass
+ # for 'Generic' and ABCs below.
'ByteString',
'Container',
'Hashable',
@@ -145,7 +147,7 @@
class _TypingBase(metaclass=TypingMeta, _root=True):
"""Internal indicator of special typing constructs."""
- __slots__ = ()
+ __slots__ = ('__weakref__',)
def __init__(self, *args, **kwds):
pass
@@ -514,7 +516,7 @@
if tvars is None:
tvars = []
- if hasattr(arg, '_subs_tree'):
+ if hasattr(arg, '_subs_tree') and isinstance(arg, (GenericMeta, _TypingBase)):
return arg._subs_tree(tvars, args)
if isinstance(arg, TypeVar):
for i, tvar in enumerate(tvars):
@@ -523,6 +525,16 @@
return arg
+# Special typing constructs Union, Optional, Generic, Callable and Tuple
+# use three special attributes for internal bookkeeping of generic types:
+# * __parameters__ is a tuple of unique free type parameters of a generic
+# type, for example, Dict[T, T].__parameters__ == (T,);
+# * __origin__ keeps a reference to a type that was subscripted,
+# e.g., Union[T, int].__origin__ == Union;
+# * __args__ is a tuple of all arguments used in subscripting,
+# e.g., Dict[T, int].__args__ == (T, int).
+
+
def _subs_tree(cls, tvars=None, args=None):
"""An internal helper function: calculate substitution tree
for generic cls after replacing its type parameters with
@@ -757,9 +769,12 @@
return (Union,) + tree_args
def __eq__(self, other):
- if not isinstance(other, _Union):
+ if isinstance(other, _Union):
+ return self.__tree_hash__ == other.__tree_hash__
+ elif self is not Union:
return self._subs_tree() == other
- return self.__tree_hash__ == other.__tree_hash__
+ else:
+ return self is other
def __hash__(self):
return self.__tree_hash__
@@ -883,10 +898,26 @@
class GenericMeta(TypingMeta, abc.ABCMeta):
- """Metaclass for generic types."""
+ """Metaclass for generic types.
+
+ This is a metaclass for typing.Generic and generic ABCs defined in
+ typing module. User defined subclasses of GenericMeta can override
+ __new__ and invoke super().__new__. Note that GenericMeta.__new__
+ has strict rules on what is allowed in its bases argument:
+ * plain Generic is disallowed in bases;
+ * Generic[...] should appear in bases at most once;
+ * if Generic[...] is present, then it should list all type variables
+ that appear in other bases.
+ In addition, type of all generic bases is erased, e.g., C[int] is
+ stripped to plain C.
+ """
def __new__(cls, name, bases, namespace,
tvars=None, args=None, origin=None, extra=None, orig_bases=None):
+ """Create a new generic class. GenericMeta.__new__ accepts
+ keyword arguments that are used for internal bookkeeping, therefore
+ an override should pass unused keyword arguments to super().
+ """
if tvars is not None:
# Called from __getitem__() below.
assert origin is not None
@@ -1906,7 +1937,9 @@
msg = "NamedTuple('Name', [(f0, t0), (f1, t1), ...]); each t must be a type"
types = [(n, _type_check(t, msg)) for n, t in types]
nm_tpl = collections.namedtuple(name, [n for n, t in types])
- nm_tpl._field_types = dict(types)
+ # Prior to PEP 526, only _field_types attribute was assigned.
+ # Now, both __annotations__ and _field_types are used to maintain compatibility.
+ nm_tpl.__annotations__ = nm_tpl._field_types = collections.OrderedDict(types)
try:
nm_tpl.__module__ = sys._getframe(2).f_globals.get('__name__', '__main__')
except (AttributeError, ValueError):
@@ -1941,8 +1974,10 @@
Employee = collections.namedtuple('Employee', ['name', 'id'])
- The resulting class has one extra attribute: _field_types,
- giving a dict mapping field names to types. (The field names
+ The resulting class has extra __annotations__ and _field_types
+ attributes, giving an ordered dict mapping field names to types.
+ __annotations__ should be preferred, while _field_types
+ is kept to maintain pre PEP 526 compatibility. (The field names
are in the _fields attribute, which is part of the namedtuple
API.) Alternative equivalent keyword syntax is also accepted::