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

[gvanrossum]

https://github.com/python/cpython/commit/e2eeffefed32bb8c47c09bdd94e27a4e949894ef
commit: e2eeffefed32bb8c47c09bdd94e27a4e949894ef
branch: 3.10
author: Gregory Beauregard <greg at greg.red>
committer: gvanrossum <gvanrossum at gmail.com>
date: 2022-02-07T08:21:56-08:00
summary:

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

(cherry picked from commit 77b025be4a4cd5a3bfc1b1af560cc57e8e956c98)

Co-authored-by: Gregory Beauregard <greg at greg.red>

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 f13541e10d58c..341be1dd031ab 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -4768,6 +4768,11 @@ 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 abd5899806f29..7743c7f76bde8 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -165,7 +165,7 @@ 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, Final):
+    if arg in (Any, NoReturn, 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