From 77b025be4a4cd5a3bfc1b1af560cc57e8e956c98 Mon Sep 17 00:00:00 2001 From: Gregory Beauregard Date: Sun, 6 Feb 2022 15:16:22 -0800 Subject: [PATCH] bpo-46655: allow stringized TypeAlias with get_type_hints (GH-31156) --- Lib/test/test_typing.py | 5 +++++ Lib/typing.py | 2 +- .../next/Library/2022-02-06-08-54-03.bpo-46655.DiLzYv.rst | 1 + 3 files changed, 7 insertions(+), 1 deletion(-) create mode 100644 Misc/NEWS.d/next/Library/2022-02-06-08-54-03.bpo-46655.DiLzYv.rst diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py index 14f49b01aa9..2aee5c33b66 100644 --- a/Lib/test/test_typing.py +++ b/Lib/test/test_typing.py @@ -4866,6 +4866,11 @@ class TypeAliasTests(BaseTestCase): with self.assertRaises(TypeError): 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): with self.assertRaises(TypeError): issubclass(Employee, TypeAlias) diff --git a/Lib/typing.py b/Lib/typing.py index e4e32b5b320..44c239c43ee 100644 --- a/Lib/typing.py +++ b/Lib/typing.py @@ -174,7 +174,7 @@ def _type_check(arg, msg, is_argument=True, module=None, *, allow_special_forms= if (isinstance(arg, _GenericAlias) and arg.__origin__ in invalid_generic_forms): raise TypeError(f"{arg} is not valid as type argument") - if arg in (Any, NoReturn, ClassVar, Final): + if arg in (Any, NoReturn, ClassVar, Final, TypeAlias): return arg if isinstance(arg, _SpecialForm) or arg in (Generic, Protocol): raise TypeError(f"Plain {arg} is not valid as type argument") diff --git a/Misc/NEWS.d/next/Library/2022-02-06-08-54-03.bpo-46655.DiLzYv.rst b/Misc/NEWS.d/next/Library/2022-02-06-08-54-03.bpo-46655.DiLzYv.rst new file mode 100644 index 00000000000..4f0de9519a0 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2022-02-06-08-54-03.bpo-46655.DiLzYv.rst @@ -0,0 +1 @@ +In :func:`typing.get_type_hints`, support evaluating bare stringified ``TypeAlias`` annotations. Patch by Gregory Beauregard. \ No newline at end of file