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Add better default value for TypeVar default (PEP 696) #85

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Merged
merged 1 commit into from
Oct 27, 2022
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Add better default value for TypeVar default (PEP 696) #85

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5 changes: 5 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,3 +1,8 @@
# Release 4.4.1 (?)
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Might end up being 4.5.0, but we can change that later.

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We should probably just use UNRELEASED in the future.


- Add better default value for TypeVar `default` parameter, PEP 696. Enables
runtime check if `None` was passed as default. Patch by Marc Mueller (@cdce8p).

# Release 4.4.0 (October 6, 2022)

- Add `typing_extensions.Any` a backport of python 3.11's Any class which is
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6 changes: 6 additions & 0 deletions src/test_typing_extensions.py
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Expand Up @@ -3439,6 +3439,12 @@ def test_typevar(self):
class A(Generic[T]): ...
Alias = Optional[T]

def test_typevar_none(self):
U = typing_extensions.TypeVar('U')
U_None = typing_extensions.TypeVar('U_None', default=None)
self.assertEqual(U.__default__, None)
self.assertEqual(U_None.__default__, type(None))

def test_paramspec(self):
P = ParamSpec('P', default=(str, int))
self.assertEqual(P.__default__, (str, int))
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12 changes: 6 additions & 6 deletions src/typing_extensions.py
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Expand Up @@ -1157,7 +1157,7 @@ def __init__(self, default):
if isinstance(default, (tuple, list)):
self.__default__ = tuple((typing._type_check(d, "Default must be a type")
for d in default))
elif default:
elif default != _marker:
self.__default__ = typing._type_check(default, "Default must be a type")
else:
self.__default__ = None
Expand All @@ -1171,7 +1171,7 @@ class TypeVar(typing.TypeVar, _DefaultMixin, _root=True):

def __init__(self, name, *constraints, bound=None,
covariant=False, contravariant=False,
default=None, infer_variance=False):
default=_marker, infer_variance=False):
super().__init__(name, *constraints, bound=bound, covariant=covariant,
contravariant=contravariant)
_DefaultMixin.__init__(self, default)
Expand Down Expand Up @@ -1258,7 +1258,7 @@ class ParamSpec(typing.ParamSpec, _DefaultMixin, _root=True):
__module__ = 'typing'

def __init__(self, name, *, bound=None, covariant=False, contravariant=False,
default=None):
default=_marker):
super().__init__(name, bound=bound, covariant=covariant,
contravariant=contravariant)
_DefaultMixin.__init__(self, default)
Expand Down Expand Up @@ -1334,7 +1334,7 @@ def kwargs(self):
return ParamSpecKwargs(self)

def __init__(self, name, *, bound=None, covariant=False, contravariant=False,
default=None):
default=_marker):
super().__init__([self])
self.__name__ = name
self.__covariant__ = bool(covariant)
Expand Down Expand Up @@ -1850,7 +1850,7 @@ def _is_unpack(obj):
class TypeVarTuple(typing.TypeVarTuple, _DefaultMixin, _root=True):
"""Type variable tuple."""

def __init__(self, name, *, default=None):
def __init__(self, name, *, default=_marker):
super().__init__(name)
_DefaultMixin.__init__(self, default)

Expand Down Expand Up @@ -1913,7 +1913,7 @@ def get_shape(self) -> Tuple[*Ts]:
def __iter__(self):
yield self.__unpacked__

def __init__(self, name, *, default=None):
def __init__(self, name, *, default=_marker):
self.__name__ = name
_DefaultMixin.__init__(self, default)

Expand Down