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gh-92261: Disallow iteration of Union (and other special forms) (GH-92262) (GH-92582)

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(cherry picked from commit 4739997e14)

Co-authored-by: Matthew Rahtz <matthew.rahtz@gmail.com>
This commit is contained in:
Miss Islington (bot) 2022-05-09 22:39:31 -07:00 • committed by GitHub
parent 74c094d804
commit 7540a432ce
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4 changed files with 72 additions and 5 deletions
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25
Lib/typing.py
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@ -405,9 +405,24 @@ class _Immutable:
return self
class _NotIterable:
"""Mixin to prevent iteration, without being compatible with Iterable.
That is, we could do:
def __iter__(self): raise TypeError()
But this would make users of this mixin duck type-compatible with
collections.abc.Iterable - isinstance(foo, Iterable) would be True.
Luckily, we can instead prevent iteration by setting __iter__ to None, which
is treated specially.
"""
__iter__ = None
# Internal indicator of special typing constructs.
# See __doc__ instance attribute for specific docs.
class _SpecialForm(_Final, _root=True):
class _SpecialForm(_Final, _NotIterable, _root=True):
__slots__ = ('_name', '__doc__', '_getitem')
def __init__(self, getitem):
@ -1498,7 +1513,7 @@ class _GenericAlias(_BaseGenericAlias, _root=True):
# 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):
class _SpecialGenericAlias(_NotIterable, _BaseGenericAlias, _root=True):
def __init__(self, origin, nparams, *, inst=True, name=None):
if name is None:
name = origin.__name__
@ -1541,7 +1556,7 @@ class _SpecialGenericAlias(_BaseGenericAlias, _root=True):
def __ror__(self, left):
return Union[left, self]
class _CallableGenericAlias(_GenericAlias, _root=True):
class _CallableGenericAlias(_NotIterable, _GenericAlias, _root=True):
def __repr__(self):
assert self._name == 'Callable'
args = self.__args__
@ -1606,7 +1621,7 @@ class _TupleType(_SpecialGenericAlias, _root=True):
return self.copy_with(params)
class _UnionGenericAlias(_GenericAlias, _root=True):
class _UnionGenericAlias(_NotIterable, _GenericAlias, _root=True):
def copy_with(self, params):
return Union[params]
@ -2046,7 +2061,7 @@ class Protocol(Generic, metaclass=_ProtocolMeta):
cls.__init__ = _no_init_or_replace_init
class _AnnotatedAlias(_GenericAlias, _root=True):
class _AnnotatedAlias(_NotIterable, _GenericAlias, _root=True):
"""Runtime representation of an annotated type.
At its core 'Annotated[t, dec1, dec2, ...]' is an alias for the type 't'