[Python-checkins] bpo-46655: allow stringized TypeAlias with get_type_hints (GH-31156)

[gvanrossum]

https://github.com/python/cpython/commit/77b025be4a4cd5a3bfc1b1af560cc57e8e956c98
commit: 77b025be4a4cd5a3bfc1b1af560cc57e8e956c98
branch: main
author: Gregory Beauregard <greg at greg.red>
committer: gvanrossum <gvanrossum at gmail.com>
date: 2022-02-06T15:16:22-08:00
summary:

bpo-46655: allow stringized TypeAlias with get_type_hints (GH-31156)

files:
A Misc/NEWS.d/next/Library/2022-02-06-08-54-03.bpo-46655.DiLzYv.rst
M Lib/test/test_typing.py
M Lib/typing.py

diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 14f49b01aa9f0..2aee5c33b6674 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -4866,6 +4866,11 @@ def test_no_isinstance(self):
         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 e4e32b5b320d0..44c239c43ee4e 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 0000000000000..4f0de9519a00e
--- /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