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bpo-40397: Remove __args__ and __parameters__ from _SpecialGenericAlias by serhiy-storchaka · Pull Request #19984 · python/cpython · GitHub
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bpo-40397: Remove __args__ and __parameters__ from _SpecialGenericAlias #19984

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serhiy-storchaka merged 2 commits into from
May 10, 2020
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bpo-40397: Remove __args__ and __parameters__ from _SpecialGenericAlias #19984

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bpo-40397: Remove __args__ and __parameters__ from _SpecialGenericAlias
serhiy-storchaka May 7, 2020
11b10f3
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serhiy-storchaka May 10, 2020
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167 changes: 87 additions & 80 deletions Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -186,14 +186,13 @@ def _collect_type_vars(types):
return tuple(tvars)


def _check_generic(cls, parameters):
def _check_generic(cls, parameters, elen):
"""Check correct count for parameters of a generic cls (internal helper).
This gives a nice error message in case of count mismatch.
"""
if not cls.__parameters__:
if not elen:
raise TypeError(f"{cls} is not a generic class")
alen = len(parameters)
elen = len(cls.__parameters__)
if alen != elen:
raise TypeError(f"Too {'many' if alen > elen else 'few'} parameters for {cls};"
f" actual {alen}, expected {elen}")
Expand Down Expand Up @@ -592,17 +591,6 @@ def __reduce__(self):
return self.__name__


# 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, or the non-generic version of
# the type.
# * __args__ is a tuple of all arguments used in subscripting,
# e.g., Dict[T, int].__args__ == (T, int).


def _is_dunder(attr):
return attr.startswith('__') and attr.endswith('__')

Expand All @@ -615,28 +603,11 @@ class _BaseGenericAlias(_Final, _root=True):
have 'name' always set. If 'inst' is False, then the alias can't be instantiated,
this is used by e.g. typing.List and typing.Dict.
"""
def __init__(self, origin, params, *, inst=True, name=None):
def __init__(self, origin, *, inst=True, name=None):
self._inst = inst
self._name = name
if not isinstance(params, tuple):
params = (params,)
self.__origin__ = origin
self.__args__ = tuple(... if a is _TypingEllipsis else
() if a is _TypingEmpty else
a for a in params)
self.__parameters__ = _collect_type_vars(params)
self.__slots__ = None # This is not documented.
if not name:
self.__module__ = origin.__module__

def __eq__(self, other):
if not isinstance(other, _BaseGenericAlias):
return NotImplemented
return (self.__origin__ == other.__origin__
and self.__args__ == other.__args__)

def __hash__(self):
return hash((self.__origin__, self.__args__))

def __call__(self, *args, **kwargs):
if not self._inst:
Expand Down Expand Up @@ -669,7 +640,7 @@ def __getattr__(self, attr):
raise AttributeError(attr)

def __setattr__(self, attr, val):
if _is_dunder(attr) or attr in ('_name', '_inst'):
if _is_dunder(attr) or attr in ('_name', '_inst', '_nparams'):
super().__setattr__(attr, val)
else:
setattr(self.__origin__, attr, val)
Expand All @@ -682,7 +653,38 @@ def __subclasscheck__(self, cls):
" class and instance checks")


# 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, or the non-generic version of
# the type.
# * __args__ is a tuple of all arguments used in subscripting,
# e.g., Dict[T, int].__args__ == (T, int).


class _GenericAlias(_BaseGenericAlias, _root=True):
def __init__(self, origin, params, *, inst=True, name=None):
super().__init__(origin, inst=inst, name=name)
if not isinstance(params, tuple):
params = (params,)
self.__args__ = tuple(... if a is _TypingEllipsis else
() if a is _TypingEmpty else
a for a in params)
self.__parameters__ = _collect_type_vars(params)
if not name:
self.__module__ = origin.__module__

def __eq__(self, other):
if not isinstance(other, _GenericAlias):
return NotImplemented
return (self.__origin__ == other.__origin__
and self.__args__ == other.__args__)

def __hash__(self):
return hash((self.__origin__, self.__args__))

@_tp_cache
def __getitem__(self, params):
if self.__origin__ in (Generic, Protocol):
Expand All @@ -692,14 +694,14 @@ def __getitem__(self, params):
params = (params,)
msg = "Parameters to generic types must be types."
params = tuple(_type_check(p, msg) for p in params)
_check_generic(self, params)
_check_generic(self, params, len(self.__parameters__))

subst = dict(zip(self.__parameters__, params))
new_args = []
for arg in self.__args__:
if isinstance(arg, TypeVar):
arg = subst[arg]
elif isinstance(arg, (_BaseGenericAlias, GenericAlias)):
elif isinstance(arg, (_GenericAlias, GenericAlias)):
subargs = tuple(subst[x] for x in arg.__parameters__)
arg = arg[subargs]
new_args.append(arg)
Expand Down Expand Up @@ -739,11 +741,16 @@ def __mro_entries__(self, bases):
return (self.__origin__,)


# _nparams is the number of accepted parameters, e.g. 0 for Hashable,
# 1 for List and 2 for Dict. It may be -1 if variable number of
# parameters are accepted (needs custom __getitem__).

class _SpecialGenericAlias(_BaseGenericAlias, _root=True):
def __init__(self, origin, params, *, inst=True, name=None):
def __init__(self, origin, nparams, *, inst=True, name=None):

ilevkivskyi May 7, 2020

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality Hide comment

Maybe add a docstring/comment explaining the role of nparams/self._nparams?
if name is None:
name = origin.__name__
super().__init__(origin, params, inst=inst, name=name)
super().__init__(origin, inst=inst, name=name)
self._nparams = nparams
self.__doc__ = f'A generic version of {origin.__module__}.{origin.__qualname__}'

@_tp_cache
Expand All @@ -752,8 +759,7 @@ def __getitem__(self, params):
params = (params,)
msg = "Parameters to generic types must be types."
params = tuple(_type_check(p, msg) for p in params)
_check_generic(self, params)
assert self.__args__ == self.__parameters__
_check_generic(self, params, self._nparams)
return self.copy_with(params)

def copy_with(self, params):
Expand Down Expand Up @@ -912,7 +918,7 @@ def __class_getitem__(cls, params):
f"Parameters to {cls.__name__}[...] must all be unique")
else:
# Subscripting a regular Generic subclass.
_check_generic(cls, params)
_check_generic(cls, params, len(cls.__parameters__))
return _GenericAlias(cls, params)

def __init_subclass__(cls, *args, **kwargs):
Expand Down Expand Up @@ -1571,18 +1577,18 @@ class Other(Leaf): # Error reported by type checker
# Various ABCs mimicking those in collections.abc.
_alias = _SpecialGenericAlias

Hashable = _alias(collections.abc.Hashable, ()) # Not generic.
Awaitable = _alias(collections.abc.Awaitable, T_co)
Coroutine = _alias(collections.abc.Coroutine, (T_co, T_contra, V_co))
AsyncIterable = _alias(collections.abc.AsyncIterable, T_co)
AsyncIterator = _alias(collections.abc.AsyncIterator, T_co)
Iterable = _alias(collections.abc.Iterable, T_co)
Iterator = _alias(collections.abc.Iterator, T_co)
Reversible = _alias(collections.abc.Reversible, T_co)
Sized = _alias(collections.abc.Sized, ()) # Not generic.
Container = _alias(collections.abc.Container, T_co)
Collection = _alias(collections.abc.Collection, T_co)
Callable = _CallableType(collections.abc.Callable, ())
Hashable = _alias(collections.abc.Hashable, 0) # Not generic.
Awaitable = _alias(collections.abc.Awaitable, 1)
Coroutine = _alias(collections.abc.Coroutine, 3)
AsyncIterable = _alias(collections.abc.AsyncIterable, 1)
AsyncIterator = _alias(collections.abc.AsyncIterator, 1)
Iterable = _alias(collections.abc.Iterable, 1)
Iterator = _alias(collections.abc.Iterator, 1)
Reversible = _alias(collections.abc.Reversible, 1)
Sized = _alias(collections.abc.Sized, 0) # Not generic.
Container = _alias(collections.abc.Container, 1)
Collection = _alias(collections.abc.Collection, 1)
Callable = _CallableType(collections.abc.Callable, 2)
Callable.__doc__ = \
"""Callable type; Callable[[int], str] is a function of (int) -> str.

Expand All @@ -1593,15 +1599,16 @@ class Other(Leaf): # Error reported by type checker
There is no syntax to indicate optional or keyword arguments,
such function types are rarely used as callback types.
"""
AbstractSet = _alias(collections.abc.Set, T_co, name='AbstractSet')
MutableSet = _alias(collections.abc.MutableSet, T)
AbstractSet = _alias(collections.abc.Set, 1, name='AbstractSet')
MutableSet = _alias(collections.abc.MutableSet, 1)
# NOTE: Mapping is only covariant in the value type.
Mapping = _alias(collections.abc.Mapping, (KT, VT_co))
MutableMapping = _alias(collections.abc.MutableMapping, (KT, VT))
Sequence = _alias(collections.abc.Sequence, T_co)
MutableSequence = _alias(collections.abc.MutableSequence, T)
ByteString = _alias(collections.abc.ByteString, ()) # Not generic
Tuple = _TupleType(tuple, (), inst=False, name='Tuple')
Mapping = _alias(collections.abc.Mapping, 2)
MutableMapping = _alias(collections.abc.MutableMapping, 2)
Sequence = _alias(collections.abc.Sequence, 1)
MutableSequence = _alias(collections.abc.MutableSequence, 1)
ByteString = _alias(collections.abc.ByteString, 0) # Not generic
# Tuple accepts variable number of parameters.
Tuple = _TupleType(tuple, -1, inst=False, name='Tuple')
Tuple.__doc__ = \
"""Tuple type; Tuple[X, Y] is the cross-product type of X and Y.

Expand All @@ -1611,24 +1618,24 @@ class Other(Leaf): # Error reported by type checker

To specify a variable-length tuple of homogeneous type, use Tuple[T, ...].
"""
List = _alias(list, T, inst=False, name='List')
Deque = _alias(collections.deque, T, name='Deque')
Set = _alias(set, T, inst=False, name='Set')
FrozenSet = _alias(frozenset, T_co, inst=False, name='FrozenSet')
MappingView = _alias(collections.abc.MappingView, T_co)
KeysView = _alias(collections.abc.KeysView, KT)
ItemsView = _alias(collections.abc.ItemsView, (KT, VT_co))
ValuesView = _alias(collections.abc.ValuesView, VT_co)
ContextManager = _alias(contextlib.AbstractContextManager, T_co, name='ContextManager')
AsyncContextManager = _alias(contextlib.AbstractAsyncContextManager, T_co, name='AsyncContextManager')
Dict = _alias(dict, (KT, VT), inst=False, name='Dict')
DefaultDict = _alias(collections.defaultdict, (KT, VT), name='DefaultDict')
OrderedDict = _alias(collections.OrderedDict, (KT, VT))
Counter = _alias(collections.Counter, T)
ChainMap = _alias(collections.ChainMap, (KT, VT))
Generator = _alias(collections.abc.Generator, (T_co, T_contra, V_co))
AsyncGenerator = _alias(collections.abc.AsyncGenerator, (T_co, T_contra))
Type = _alias(type, CT_co, inst=False, name='Type')
List = _alias(list, 1, inst=False, name='List')
Deque = _alias(collections.deque, 1, name='Deque')
Set = _alias(set, 1, inst=False, name='Set')
FrozenSet = _alias(frozenset, 1, inst=False, name='FrozenSet')
MappingView = _alias(collections.abc.MappingView, 1)
KeysView = _alias(collections.abc.KeysView, 1)
ItemsView = _alias(collections.abc.ItemsView, 2)
ValuesView = _alias(collections.abc.ValuesView, 1)
ContextManager = _alias(contextlib.AbstractContextManager, 1, name='ContextManager')
AsyncContextManager = _alias(contextlib.AbstractAsyncContextManager, 1, name='AsyncContextManager')
Dict = _alias(dict, 2, inst=False, name='Dict')
DefaultDict = _alias(collections.defaultdict, 2, name='DefaultDict')
OrderedDict = _alias(collections.OrderedDict, 2)
Counter = _alias(collections.Counter, 1)
ChainMap = _alias(collections.ChainMap, 2)
Generator = _alias(collections.abc.Generator, 3)
AsyncGenerator = _alias(collections.abc.AsyncGenerator, 2)
Type = _alias(type, 1, inst=False, name='Type')
Type.__doc__ = \
"""A special construct usable to annotate class objects.

Expand Down Expand Up @@ -2122,8 +2129,8 @@ class io:
io.__name__ = __name__ + '.io'
sys.modules[io.__name__] = io

Pattern = _alias(stdlib_re.Pattern, AnyStr)
Match = _alias(stdlib_re.Match, AnyStr)
Pattern = _alias(stdlib_re.Pattern, 1)
Match = _alias(stdlib_re.Match, 1)

class re:
"""Wrapper namespace for re type aliases."""
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2020-05-07-21-22-04.bpo-40397.PVWFAn.rst
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@@ -0,0 +1,2 @@
Removed attributes ``__args__`` and ``__parameters__`` from special generic
aliases like ``typing.List`` (not subscripted).
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