From ffbdf1a95c88ad37ef0aeb20c54e75358961c512 Mon Sep 17 00:00:00 2001
From: Eric Mark Martin <ericmarkmartin@gmail.com>
Date: Thu, 30 Apr 2026 01:51:59 -0400
Subject: [PATCH 1/3] Make TypeAliasType __module__ writable

---
 src/test_typing_extensions.py | 11 ++++++-----
 src/typing_extensions.py      |  4 ++--
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/test_typing_extensions.py b/src/test_typing_extensions.py
index f07e1eb0..34469068 100644
--- a/src/test_typing_extensions.py
+++ b/src/test_typing_extensions.py
@@ -8244,11 +8244,12 @@ def test_cannot_set_attributes(self):
             "attribute '__parameters__' of 'typing.TypeAliasType' objects is not writable",
         ):
             Simple.__parameters__ = (T,)
-        with self.assertRaisesRegex(
-            AttributeError,
-            "attribute '__module__' of 'typing.TypeAliasType' objects is not writable",
-        ):
-            Simple.__module__ = 42
+
+        # __module__ is the exception---it's assignable
+        module_sentinel = object()
+        Simple.__module__ = module_sentinel
+        self.assertIs(Simple.__module__, module_sentinel)
+
         with self.assertRaisesRegex(
             AttributeError,
             "'typing.TypeAliasType' object has no attribute 'some_attribute'",
diff --git a/src/typing_extensions.py b/src/typing_extensions.py
index 20c331ee..4c042ac8 100644
--- a/src/typing_extensions.py
+++ b/src/typing_extensions.py
@@ -3733,7 +3733,7 @@ def __init__(self, name: str, value, *, type_params=()):
             self.__name__ = name
 
         def __setattr__(self, name: str, value: object, /) -> None:
-            if hasattr(self, "__name__"):
+            if hasattr(self, "__name__") and name != "__module__":
                 self._raise_attribute_error(name)
             super().__setattr__(name, value)
 
@@ -3744,7 +3744,7 @@ def _raise_attribute_error(self, name: str) -> Never:
             # Match the Python 3.12 error messages exactly
             if name == "__name__":
                 raise AttributeError("readonly attribute")
-            elif name in {"__value__", "__type_params__", "__parameters__", "__module__"}:
+            elif name in {"__value__", "__type_params__", "__parameters__"}:
                 raise AttributeError(
                     f"attribute '{name}' of 'typing.TypeAliasType' objects "
                     "is not writable"

From a1d42373df142761977583819809dc0e7434486e Mon Sep 17 00:00:00 2001
From: Eric Mark Martin <ericmarkmartin@gmail.com>
Date: Thu, 30 Apr 2026 13:16:14 -0400
Subject: [PATCH 2/3] add changelog entry

---
 CHANGELOG.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 733505a5..80a1775e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Unreleased
 
+- Make `typing_extensions.TypeAliasType`'s `__module__` attribute writable.
+  Backport of CPython PR
+  [#149172](https://github.com/python/cpython/pull/149172).
 - Fix incorrect behaviour on Python 3.9 and Python 3.10 that meant that
   calling `isinstance` with `typing_extensions.Concatenate[...]` or
   `typing_extensions.Unpack[...]` as the first argument could have a different

From 21ae3906da24a97e74c1c706cc3cff103aa325e3 Mon Sep 17 00:00:00 2001
From: Eric Mark Martin <ericmarkmartin@gmail.com>
Date: Thu, 30 Apr 2026 13:17:22 -0400
Subject: [PATCH 3/3] bump TypeAliasType re-export guard

---
 src/test_typing_extensions.py | 2 +-
 src/typing_extensions.py      | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/test_typing_extensions.py b/src/test_typing_extensions.py
index 34469068..2719ec80 100644
--- a/src/test_typing_extensions.py
+++ b/src/test_typing_extensions.py
@@ -7072,7 +7072,7 @@ def test_typing_extensions_defers_when_possible(self):
                 'AsyncGenerator', 'ContextManager', 'AsyncContextManager',
                 'ParamSpec', 'TypeVar', 'TypeVarTuple', 'get_type_hints',
             }
-        if sys.version_info < (3, 14):
+        if sys.version_info < (3, 15):
             exclude |= {
                 'TypeAliasType'
             }
diff --git a/src/typing_extensions.py b/src/typing_extensions.py
index 4c042ac8..d4a95678 100644
--- a/src/typing_extensions.py
+++ b/src/typing_extensions.py
@@ -3613,14 +3613,14 @@ def __ror__(self, other):
                 return typing.Union[other, self]
 
 
-# Breakpoint: https://github.com/python/cpython/pull/124795
-if sys.version_info >= (3, 14):
+# Breakpoint: https://github.com/python/cpython/pull/149172
+if sys.version_info >= (3, 15):
     TypeAliasType = typing.TypeAliasType
-# <=3.13
+# <=3.14
 else:
     # Breakpoint: https://github.com/python/cpython/pull/103764
     if sys.version_info >= (3, 12):
-        # 3.12-3.13
+        # 3.12-3.14
         def _is_unionable(obj):
             """Corresponds to is_unionable() in unionobject.c in CPython."""
             return obj is None or isinstance(obj, (