6 files changed, 50 insertions, 11 deletions
diff --git a/Doc/library/collections.abc.rst b/Doc/library/collections.abc.rst
index 0abc87f919..2c941b4774 100644
--- a/Doc/library/collections.abc.rst
+++ b/Doc/library/collections.abc.rst
@@ -104,6 +104,9 @@ example, knowing that a class supplies ``__getitem__``, ``__len__``, and
 ``__iter__`` is insufficient for distinguishing a :class:`Sequence` from
 a :class:`Mapping`.
 
+.. versionadded:: 3.9
+   These abstract classes now support ``[]``. See :ref:`types-genericalias`
+   and :pep:`585`.
 
 .. _collections-abstract-base-classes:
 
diff --git a/Doc/library/datetime.rst b/Doc/library/datetime.rst
index 196aa84473..0f8b70cded 100644
--- a/Doc/library/datetime.rst
+++ b/Doc/library/datetime.rst
@@ -27,6 +27,9 @@ on efficient attribute extraction for output formatting and manipulation.
    Module :mod:`time`
       Time access and conversions.
 
+   Module :mod:`zoneinfo`
+      Concrete time zones representing the IANA time zone database.
+
    Package `dateutil <https://dateutil.readthedocs.io/en/stable/>`_
       Third-party library with expanded time zone and parsing support.
 
@@ -2174,14 +2177,13 @@ only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)).
 
 .. seealso::
 
-   `dateutil.tz <https://dateutil.readthedocs.io/en/stable/tz.html>`_
+    :mod:`zoneinfo`
       The :mod:`datetime` module has a basic :class:`timezone` class (for
       handling arbitrary fixed offsets from UTC) and its :attr:`timezone.utc`
       attribute (a UTC timezone instance).
 
-      *dateutil.tz* library brings the *IANA timezone database*
-      (also known as the Olson database) to Python, and its usage is
-      recommended.
+      ``zoneinfo`` brings the *IANA timezone database* (also known as the Olson
+      database) to Python, and its usage is recommended.
 
    `IANA timezone database <https://www.iana.org/time-zones>`_
       The Time Zone Database (often called tz, tzdata or zoneinfo) contains code
diff --git a/Doc/library/enum.rst b/Doc/library/enum.rst
index 2d80a52193..eb5ffd0c5d 100644
--- a/Doc/library/enum.rst
+++ b/Doc/library/enum.rst
@@ -1127,7 +1127,7 @@ _Private__names
 
 :ref:`Private names <private-name-mangling>` will be normal attributes in Python
 3.11 instead of either an error or a member (depending on if the name ends with
-an underscore). Using these names in 3.9 will issue a :exc:`DeprecationWarning`.
+an underscore). Using these names in 3.10 will issue a :exc:`DeprecationWarning`.
 
 
 ``Enum`` member type
@@ -1150,6 +1150,10 @@ all-uppercase names for members)::
     >>> FieldTypes.size.value
     2
 
+.. note::
+
+   This behavior is deprecated and will be removed in 3.12.
+
 .. versionchanged:: 3.5
 
 
@@ -1200,3 +1204,9 @@ all named flags and all named combinations of flags that are in the value::
     >>> Color(7)      # not named combination
     <Color.CYAN|MAGENTA|BLUE|YELLOW|GREEN|RED: 7>
 
+.. note::
+
+   In 3.11 unnamed combinations of flags will only produce the canonical flag
+   members (aka single-value flags).  So ``Color(7)`` will produce something
+   like ``<Color.BLUE|GREEN|RED: 7>``.
+
diff --git a/Doc/library/exceptions.rst b/Doc/library/exceptions.rst
index 1a883ba19a..f8a692e812 100644
--- a/Doc/library/exceptions.rst
+++ b/Doc/library/exceptions.rst
@@ -34,6 +34,10 @@ class or one of its subclasses, and not from :exc:`BaseException`.  More
 information on defining exceptions is available in the Python Tutorial under
 :ref:`tut-userexceptions`.
 
+
+Exception context
+-----------------
+
 When raising (or re-raising) an exception in an :keyword:`except` or
 :keyword:`finally` clause
 :attr:`__context__` is automatically set to the last exception caught; if the
@@ -67,6 +71,25 @@ exceptions so that the final line of the traceback always shows the last
 exception that was raised.
 
 
+Inheriting from built-in exceptions
+-----------------------------------
+
+User code can create subclasses that inherit from an exception type.
+It's recommended to only subclass one exception type at a time to avoid
+any possible conflicts between how the bases handle the ``args``
+attribute, as well as due to possible memory layout incompatibilities.
+
+.. impl-detail::
+
+   Most built-in exceptions are implemented in C for efficiency, see:
+   :source:`Objects/exceptions.c`.  Some have custom memory layouts
+   which makes it impossible to create a subclass that inherits from
+   multiple exception types. The memory layout of a type is an implementation
+   detail and might change between Python versions, leading to new
+   conflicts in the future.  Therefore, it's recommended to avoid
+   subclassing multiple exception types altogether.
+
+
 Base classes
 ------------
 
diff --git a/Doc/library/random.rst b/Doc/library/random.rst
index e924127d8b..b9c33af59c 100644
--- a/Doc/library/random.rst
+++ b/Doc/library/random.rst
@@ -512,7 +512,7 @@ between the effects of a drug versus a placebo::
 
 Simulation of arrival times and service deliveries for a multiserver queue::
 
-    from heapq import heappush, heappop
+    from heapq import heapify, heapreplace
     from random import expovariate, gauss
     from statistics import mean, quantiles
 
@@ -524,14 +524,15 @@ Simulation of arrival times and service deliveries for a multiserver queue::
     waits = []
     arrival_time = 0.0
     servers = [0.0] * num_servers  # time when each server becomes available
-    for i in range(100_000):
+    heapify(servers)
+    for i in range(1_000_000):
         arrival_time += expovariate(1.0 / average_arrival_interval)
-        next_server_available = heappop(servers)
+        next_server_available = servers[0]
         wait = max(0.0, next_server_available - arrival_time)
         waits.append(wait)
-        service_duration = gauss(average_service_time, stdev_service_time)
+        service_duration = max(0.0, gauss(average_service_time, stdev_service_time))
         service_completed = arrival_time + wait + service_duration
-        heappush(servers, service_completed)
+        heapreplace(servers, service_completed)
 
     print(f'Mean wait: {mean(waits):.1f}   Max wait: {max(waits):.1f}')
     print('Quartiles:', [round(q, 1) for q in quantiles(waits)])
diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst
index 13760c1921..c402c73b48 100644
--- a/Doc/library/typing.rst
+++ b/Doc/library/typing.rst
@@ -19,7 +19,7 @@
 
 This module provides runtime support for type hints as specified by
 :pep:`484`, :pep:`526`, :pep:`544`, :pep:`586`, :pep:`589`, :pep:`591`,
-:pep:`612` and :pep:`613`.
+:pep:`593`, :pep:`612`, :pep:`613` and :pep:`647`.
 The most fundamental support consists of the types :data:`Any`, :data:`Union`,
 :data:`Tuple`, :data:`Callable`, :class:`TypeVar`, and
 :class:`Generic`.  For full specification please see :pep:`484`.  For