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[3.10] bpo-46655: allow stringized TypeAlias with get_type_hints (GH-31156). (#31175)

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(cherry picked from commit 77b025be4a)

Co-authored-by: Gregory Beauregard <greg@greg.red>
This commit is contained in:
Gregory Beauregard 2022-02-07 08:21:56 -08:00 • committed by GitHub
parent c1ff4cb98b
commit e2eeffefed
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3 changed files with 7 additions and 1 deletions
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5
Lib/test/test_typing.py
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@ -4768,6 +4768,11 @@ def test_no_isinstance(self):
with self.assertRaises(TypeError): with self.assertRaises(TypeError):
isinstance(42, TypeAlias) isinstance(42, TypeAlias)
def test_stringized_usage(self):
class A:
a: "TypeAlias"
self.assertEqual(get_type_hints(A), {'a': TypeAlias})
def test_no_issubclass(self): def test_no_issubclass(self):
with self.assertRaises(TypeError): with self.assertRaises(TypeError):
issubclass(Employee, TypeAlias) issubclass(Employee, TypeAlias)

2
Lib/typing.py
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@ -165,7 +165,7 @@ def _type_check(arg, msg, is_argument=True, module=None, *, allow_special_forms=
if (isinstance(arg, _GenericAlias) and if (isinstance(arg, _GenericAlias) and
arg.__origin__ in invalid_generic_forms): arg.__origin__ in invalid_generic_forms):
raise TypeError(f"{arg} is not valid as type argument") raise TypeError(f"{arg} is not valid as type argument")
if arg in (Any, NoReturn, Final): if arg in (Any, NoReturn, Final, TypeAlias):
return arg return arg
if isinstance(arg, _SpecialForm) or arg in (Generic, Protocol): if isinstance(arg, _SpecialForm) or arg in (Generic, Protocol):
raise TypeError(f"Plain {arg} is not valid as type argument") raise TypeError(f"Plain {arg} is not valid as type argument")

1
Misc/NEWS.d/next/Library/2022-02-06-08-54-03.bpo-46655.DiLzYv.rst Normal file
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@ -0,0 +1 @@
In :func:`typing.get_type_hints`, support evaluating bare stringified ``TypeAlias`` annotations. Patch by Gregory Beauregard.