From c70742eb18248f023d6496a6428a776eebc77979 Mon Sep 17 00:00:00 2001
From: AlexWaygood <alex.waygood@gmail.com>
Date: Wed, 22 Mar 2023 22:40:41 +0000
Subject: [PATCH 1/2] Typing: document performance pitfalls of protocols
 decorated with `@runtime_checkable`

---
 Doc/library/typing.rst | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst
index 80a969e6335abe..297e3bc9c51155 100644
--- a/Doc/library/typing.rst
+++ b/Doc/library/typing.rst
@@ -1584,16 +1584,31 @@ These are not used in annotations. They are building blocks for creating generic
 
       assert isinstance(open('/some/file'), Closable)
 
+      @runtime_checkable
+      class HasErrNo(Protocol):
+          errno: int
+
+      assert isinstance(OSError(42, 'foo'), HasErrNo)
+
    .. note::
 
-        :func:`runtime_checkable` will check only the presence of the required
-        methods, not their type signatures. For example, :class:`ssl.SSLObject`
+        :func:`!runtime_checkable` will check only the presence of the required
+        methods or attributes, not their type signatures or types.
+        For example, :class:`ssl.SSLObject`
         is a class, therefore it passes an :func:`issubclass`
         check against :data:`Callable`.  However, the
         ``ssl.SSLObject.__init__`` method exists only to raise a
         :exc:`TypeError` with a more informative message, therefore making
         it impossible to call (instantiate) :class:`ssl.SSLObject`.
 
+   .. note::
+
+        An :func:`isinstance` check against a runtime-checkable protocol can be
+        surprisingly slow compared to an ``isinstance()`` check against
+        a non-protocol class. Consider using alternative idioms such as
+        :func:`hasattr` calls for structural checks in performance-sensitive
+        code.
+
    .. versionadded:: 3.8
 
 Other special directives

From 7666617ed53eaa6d1dabc3e7672dec8872d9f4d8 Mon Sep 17 00:00:00 2001
From: AlexWaygood <alex.waygood@gmail.com>
Date: Thu, 23 Mar 2023 13:42:03 +0000
Subject: [PATCH 2/2] A thread named Bob

---
 Doc/library/typing.rst | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst
index 297e3bc9c51155..08ffa0310f0f23 100644
--- a/Doc/library/typing.rst
+++ b/Doc/library/typing.rst
@@ -1585,10 +1585,11 @@ These are not used in annotations. They are building blocks for creating generic
       assert isinstance(open('/some/file'), Closable)
 
       @runtime_checkable
-      class HasErrNo(Protocol):
-          errno: int
+      class Named(Protocol):
+          name: str
 
-      assert isinstance(OSError(42, 'foo'), HasErrNo)
+      import threading
+      assert isinstance(threading.Thread(name='Bob'), Named)
 
    .. note::