From 83464c7de5e10e10741caeb8d878337a9dd80b8a Mon Sep 17 00:00:00 2001
From: a-eT <32207200078@e.gzhu.edu.cn>
Date: Sat, 29 Nov 2025 22:18:20 +0800
Subject: [PATCH 1/8] gh-142085: Fix ChainMap.__ior__ to return NotImplemented
 for unsupported types

---
 Lib/collections/__init__.py  |  5 ++++-
 Lib/test/test_collections.py | 15 ++++++++++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
index 55ffc36ea5b0c7..6bea12bb6bde65 100644
--- a/Lib/collections/__init__.py
+++ b/Lib/collections/__init__.py
@@ -1151,7 +1151,10 @@ def clear(self):
         self.maps[0].clear()
 
     def __ior__(self, other):
-        self.maps[0].update(other)
+        try:
+            self.maps[0].update(other)
+        except TypeError:
+            return NotImplemented
         return self
 
     def __or__(self, other):
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 22595239252814..50cbcdbddf62d9 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -308,7 +308,20 @@ def __ror__(self, other):
         tmp = ChainMap() | SubclassRor()
         self.assertIs(type(tmp), SubclassRor)
         self.assertIs(type(tmp.maps[0]), dict)
-
+        
+    def test_ior_fallback(self):
+        # Verify that __ior__ returns NotImplemented for unrecognized types,
+        # allowing the other operand to handle the operation via __ror__.
+        class Rescuer:
+            def __ror__(self, other):
+                return "fallback"
+        
+        cm = ChainMap()
+        # This should not raise TypeError.
+        # Since ChainMap.__ior__ returns NotImplemented, Python calls Rescuer.__ror__,
+        # and the result ("fallback") is assigned back to 'cm'.
+        cm |= Rescuer()
+        self.assertEqual(cm, "fallback")
 
 ################################################################################
 ### Named Tuples

From b9881751825dca075a652f15291796b06b2dd938 Mon Sep 17 00:00:00 2001
From: a-eT <32207200078@e.gzhu.edu.cn>
Date: Sat, 29 Nov 2025 22:27:13 +0800
Subject: [PATCH 2/8] Add news entry for gh-142085

---
 Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst

diff --git a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst
new file mode 100644
index 00000000000000..37d1012071fb56
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst
@@ -0,0 +1 @@
+Fix :meth:~collections.ChainMap.__ior__ to return :const:NotImplemented instead of raising :exc:TypeError for unsupported types.

From f2826a9c2932b3f3a55b80c03babcc6988bc03af Mon Sep 17 00:00:00 2001
From: a-eT <32207200078@e.gzhu.edu.cn>
Date: Sat, 29 Nov 2025 22:40:28 +0800
Subject: [PATCH 3/8] Fix news entry format and encoding

---
 .../next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst  | 1 +
 Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
 delete mode 100644 Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst

diff --git a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
new file mode 100644
index 00000000000000..3e32fec435d047
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
@@ -0,0 +1 @@
+Fix :meth:`~collections.ChainMap.__ior__` to return :const:`NotImplemented` instead of raising :exc:`TypeError` for unsupported types.
diff --git a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst
deleted file mode 100644
index 37d1012071fb56..00000000000000
--- a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.rst
+++ /dev/null
@@ -1 +0,0 @@
-Fix :meth:~collections.ChainMap.__ior__ to return :const:NotImplemented instead of raising :exc:TypeError for unsupported types.

From eca91f07c81819d9104a538a1e8ec4bbc3543176 Mon Sep 17 00:00:00 2001
From: a-eT <32207200078@e.gzhu.edu.cn>
Date: Sat, 29 Nov 2025 22:50:30 +0800
Subject: [PATCH 4/8] Fix trailing whitespace manually

---
 Lib/test/test_collections.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 50cbcdbddf62d9..52616116c13974 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -315,7 +315,7 @@ def test_ior_fallback(self):
         class Rescuer:
             def __ror__(self, other):
                 return "fallback"
-        
+
         cm = ChainMap()
         # This should not raise TypeError.
         # Since ChainMap.__ior__ returns NotImplemented, Python calls Rescuer.__ror__,

From 35093d6544d8bd004a43325808629e09f879c861 Mon Sep 17 00:00:00 2001
From: a-eT <32207200078@e.gzhu.edu.cn>
Date: Sat, 29 Nov 2025 22:53:56 +0800
Subject: [PATCH 5/8] Fix trailing whitespace final

---
 Lib/test/test_collections.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 52616116c13974..6b6197d4d85ae5 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -308,7 +308,7 @@ def __ror__(self, other):
         tmp = ChainMap() | SubclassRor()
         self.assertIs(type(tmp), SubclassRor)
         self.assertIs(type(tmp.maps[0]), dict)
-        
+
     def test_ior_fallback(self):
         # Verify that __ior__ returns NotImplemented for unrecognized types,
         # allowing the other operand to handle the operation via __ror__.

From 465acdc0387369a11716b1944799b731b85824d5 Mon Sep 17 00:00:00 2001
From: a-eT <32207200078@e.gzhu.edu.cn>
Date: Sat, 29 Nov 2025 23:07:20 +0800
Subject: [PATCH 6/8] Fix sphinx warning in news entry

---
 .../next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
index 3e32fec435d047..063c1dd23e48ae 100644
--- a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
+++ b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
@@ -1 +1 @@
-Fix :meth:`~collections.ChainMap.__ior__` to return :const:`NotImplemented` instead of raising :exc:`TypeError` for unsupported types.
+Fix ``ChainMap.__ior__`` to return ``NotImplemented`` instead of raising ``TypeError`` for unsupported types.

From 78bd649df53b6fd68ce4526b782823882aacaf38 Mon Sep 17 00:00:00 2001
From: Fatin <32006697+ChuheLin@users.noreply.github.com>
Date: Sat, 29 Nov 2025 23:23:15 +0800
Subject: [PATCH 7/8] Update
 Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
---
 .../Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst     | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
index 063c1dd23e48ae..e0a268e5f79144 100644
--- a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
+++ b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
@@ -1 +1,2 @@
-Fix ``ChainMap.__ior__`` to return ``NotImplemented`` instead of raising ``TypeError`` for unsupported types.
+Fix :class:`ChainMap.__ior__ <collections.ChainMap>` to return :data:`NotImplemented`
+instead of raising :exc:`TypeError`` for unsupported types.

From d3acacf46a9c593270d276163b6387d6b88c28d0 Mon Sep 17 00:00:00 2001
From: Fatin <32006697+ChuheLin@users.noreply.github.com>
Date: Sat, 29 Nov 2025 23:30:56 +0800
Subject: [PATCH 8/8] Update
 Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
---
 .../next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
index e0a268e5f79144..d931ed6ec51a5b 100644
--- a/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
+++ b/Misc/NEWS.d/next/Library/2025-11-29-22-23-00.gh-issue-142085.7u8i9o.rst
@@ -1,2 +1,2 @@
 Fix :class:`ChainMap.__ior__ <collections.ChainMap>` to return :data:`NotImplemented`
-instead of raising :exc:`TypeError`` for unsupported types.
+instead of raising :exc:`TypeError` for unsupported types.