Issue #24254: Drop cls.__definition_order__.

4 files changed, 184 insertions, 212 deletions

diff --git a/Doc/library/inspect.rst b/Doc/library/inspect.rst
index 1977d88..5cb7c22 100644
--- a/Doc/library/inspect.rst
+++ b/Doc/library/inspect.rst
@@ -34,190 +34,185 @@ provided as convenient choices for the second argument to :func:`getmembers`.
 They also help you determine when you can expect to find the following special
 attributes:
 
-+-----------+----------------------+---------------------------+
-| Type      | Attribute            | Description               |
-+===========+======================+===========================+
-| module    | __doc__              | documentation string      |
-+-----------+----------------------+---------------------------+
-|           | __file__             | filename (missing for     |
-|           |                      | built-in modules)         |
-+-----------+----------------------+---------------------------+
-| class     | __doc__              | documentation string      |
-+-----------+----------------------+---------------------------+
-|           | __name__             | name with which this      |
-|           |                      | class was defined         |
-+-----------+----------------------+---------------------------+
-|           | __qualname__         | qualified name            |
-+-----------+----------------------+---------------------------+
-|           | __module__           | name of module in which   |
-|           |                      | this class was defined    |
-+-----------+----------------------+---------------------------+
-|           | __definition_order__ | the names of the class's  |
-|           |                      | attributes, in the order  |
-|           |                      | in which they were        |
-|           |                      | defined (if known)        |
-+-----------+----------------------+---------------------------+
-| method    | __doc__              | documentation string      |
-+-----------+----------------------+---------------------------+
-|           | __name__             | name with which this      |
-|           |                      | method was defined        |
-+-----------+----------------------+---------------------------+
-|           | __qualname__         | qualified name            |
-+-----------+----------------------+---------------------------+
-|           | __func__             | function object           |
-|           |                      | containing implementation |
-|           |                      | of method                 |
-+-----------+----------------------+---------------------------+
-|           | __self__             | instance to which this    |
-|           |                      | method is bound, or       |
-|           |                      | ``None``                  |
-+-----------+----------------------+---------------------------+
-| function  | __doc__              | documentation string      |
-+-----------+----------------------+---------------------------+
-|           | __name__             | name with which this      |
-|           |                      | function was defined      |
-+-----------+----------------------+---------------------------+
-|           | __qualname__         | qualified name            |
-+-----------+----------------------+---------------------------+
-|           | __code__             | code object containing    |
-|           |                      | compiled function         |
-|           |                      | :term:`bytecode`          |
-+-----------+----------------------+---------------------------+
-|           | __defaults__         | tuple of any default      |
-|           |                      | values for positional or  |
-|           |                      | keyword parameters        |
-+-----------+----------------------+---------------------------+
-|           | __kwdefaults__       | mapping of any default    |
-|           |                      | values for keyword-only   |
-|           |                      | parameters                |
-+-----------+----------------------+---------------------------+
-|           | __globals__          | global namespace in which |
-|           |                      | this function was defined |
-+-----------+----------------------+---------------------------+
-|           | __annotations__      | mapping of parameters     |
-|           |                      | names to annotations;     |
-|           |                      | ``"return"`` key is       |
-|           |                      | reserved for return       |
-|           |                      | annotations.              |
-+-----------+----------------------+---------------------------+
-| traceback | tb_frame             | frame object at this      |
-|           |                      | level                     |
-+-----------+----------------------+---------------------------+
-|           | tb_lasti             | index of last attempted   |
-|           |                      | instruction in bytecode   |
-+-----------+----------------------+---------------------------+
-|           | tb_lineno            | current line number in    |
-|           |                      | Python source code        |
-+-----------+----------------------+---------------------------+
-|           | tb_next              | next inner traceback      |
-|           |                      | object (called by this    |
-|           |                      | level)                    |
-+-----------+----------------------+---------------------------+
-| frame     | f_back               | next outer frame object   |
-|           |                      | (this frame's caller)     |
-+-----------+----------------------+---------------------------+
-|           | f_builtins           | builtins namespace seen   |
-|           |                      | by this frame             |
-+-----------+----------------------+---------------------------+
-|           | f_code               | code object being         |
-|           |                      | executed in this frame    |
-+-----------+----------------------+---------------------------+
-|           | f_globals            | global namespace seen by  |
-|           |                      | this frame                |
-+-----------+----------------------+---------------------------+
-|           | f_lasti              | index of last attempted   |
-|           |                      | instruction in bytecode   |
-+-----------+----------------------+---------------------------+
-|           | f_lineno             | current line number in    |
-|           |                      | Python source code        |
-+-----------+----------------------+---------------------------+
-|           | f_locals             | local namespace seen by   |
-|           |                      | this frame                |
-+-----------+----------------------+---------------------------+
-|           | f_restricted         | 0 or 1 if frame is in     |
-|           |                      | restricted execution mode |
-+-----------+----------------------+---------------------------+
-|           | f_trace              | tracing function for this |
-|           |                      | frame, or ``None``        |
-+-----------+----------------------+---------------------------+
-| code      | co_argcount          | number of arguments (not  |
-|           |                      | including \* or \*\*      |
-|           |                      | args)                     |
-+-----------+----------------------+---------------------------+
-|           | co_code              | string of raw compiled    |
-|           |                      | bytecode                  |
-+-----------+----------------------+---------------------------+
-|           | co_consts            | tuple of constants used   |
-|           |                      | in the bytecode           |
-+-----------+----------------------+---------------------------+
-|           | co_filename          | name of file in which     |
-|           |                      | this code object was      |
-|           |                      | created                   |
-+-----------+----------------------+---------------------------+
-|           | co_firstlineno       | number of first line in   |
-|           |                      | Python source code        |
-+-----------+----------------------+---------------------------+
-|           | co_flags             | bitmap: 1=optimized ``|`` |
-|           |                      | 2=newlocals ``|`` 4=\*arg |
-|           |                      | ``|`` 8=\*\*arg           |
-+-----------+----------------------+---------------------------+
-|           | co_lnotab            | encoded mapping of line   |
-|           |                      | numbers to bytecode       |
-|           |                      | indices                   |
-+-----------+----------------------+---------------------------+
-|           | co_name              | name with which this code |
-|           |                      | object was defined        |
-+-----------+----------------------+---------------------------+
-|           | co_names             | tuple of names of local   |
-|           |                      | variables                 |
-+-----------+----------------------+---------------------------+
-|           | co_nlocals           | number of local variables |
-+-----------+----------------------+---------------------------+
-|           | co_stacksize         | virtual machine stack     |
-|           |                      | space required            |
-+-----------+----------------------+---------------------------+
-|           | co_varnames          | tuple of names of         |
-|           |                      | arguments and local       |
-|           |                      | variables                 |
-+-----------+----------------------+---------------------------+
-| generator | __name__             | name                      |
-+-----------+----------------------+---------------------------+
-|           | __qualname__         | qualified name            |
-+-----------+----------------------+---------------------------+
-|           | gi_frame             | frame                     |
-+-----------+----------------------+---------------------------+
-|           | gi_running           | is the generator running? |
-+-----------+----------------------+---------------------------+
-|           | gi_code              | code                      |
-+-----------+----------------------+---------------------------+
-|           | gi_yieldfrom         | object being iterated by  |
-|           |                      | ``yield from``, or        |
-|           |                      | ``None``                  |
-+-----------+----------------------+---------------------------+
-| coroutine | __name__             | name                      |
-+-----------+----------------------+---------------------------+
-|           | __qualname__         | qualified name            |
-+-----------+----------------------+---------------------------+
-|           | cr_await             | object being awaited on,  |
-|           |                      | or ``None``               |
-+-----------+----------------------+---------------------------+
-|           | cr_frame             | frame                     |
-+-----------+----------------------+---------------------------+
-|           | cr_running           | is the coroutine running? |
-+-----------+----------------------+---------------------------+
-|           | cr_code              | code                      |
-+-----------+----------------------+---------------------------+
-| builtin   | __doc__              | documentation string      |
-+-----------+----------------------+---------------------------+
-|           | __name__             | original name of this     |
-|           |                      | function or method        |
-+-----------+----------------------+---------------------------+
-|           | __qualname__         | qualified name            |
-+-----------+----------------------+---------------------------+
-|           | __self__             | instance to which a       |
-|           |                      | method is bound, or       |
-|           |                      | ``None``                  |
-+-----------+----------------------+---------------------------+
++-----------+-----------------+---------------------------+
+| Type      | Attribute       | Description               |
++===========+=================+===========================+
+| module    | __doc__         | documentation string      |
++-----------+-----------------+---------------------------+
+|           | __file__        | filename (missing for     |
+|           |                 | built-in modules)         |
++-----------+-----------------+---------------------------+
+| class     | __doc__         | documentation string      |
++-----------+-----------------+---------------------------+
+|           | __name__        | name with which this      |
+|           |                 | class was defined         |
++-----------+-----------------+---------------------------+
+|           | __qualname__    | qualified name            |
++-----------+-----------------+---------------------------+
+|           | __module__      | name of module in which   |
+|           |                 | this class was defined    |
++-----------+-----------------+---------------------------+
+| method    | __doc__         | documentation string      |
++-----------+-----------------+---------------------------+
+|           | __name__        | name with which this      |
+|           |                 | method was defined        |
++-----------+-----------------+---------------------------+
+|           | __qualname__    | qualified name            |
++-----------+-----------------+---------------------------+
+|           | __func__        | function object           |
+|           |                 | containing implementation |
+|           |                 | of method                 |
++-----------+-----------------+---------------------------+
+|           | __self__        | instance to which this    |
+|           |                 | method is bound, or       |
+|           |                 | ``None``                  |
++-----------+-----------------+---------------------------+
+| function  | __doc__         | documentation string      |
++-----------+-----------------+---------------------------+
+|           | __name__        | name with which this      |
+|           |                 | function was defined      |
++-----------+-----------------+---------------------------+
+|           | __qualname__    | qualified name            |
++-----------+-----------------+---------------------------+
+|           | __code__        | code object containing    |
+|           |                 | compiled function         |
+|           |                 | :term:`bytecode`          |
++-----------+-----------------+---------------------------+
+|           | __defaults__    | tuple of any default      |
+|           |                 | values for positional or  |
+|           |                 | keyword parameters        |
++-----------+-----------------+---------------------------+
+|           | __kwdefaults__  | mapping of any default    |
+|           |                 | values for keyword-only   |
+|           |                 | parameters                |
++-----------+-----------------+---------------------------+
+|           | __globals__     | global namespace in which |
+|           |                 | this function was defined |
++-----------+-----------------+---------------------------+
+|           | __annotations__ | mapping of parameters     |
+|           |                 | names to annotations;     |
+|           |                 | ``"return"`` key is       |
+|           |                 | reserved for return       |
+|           |                 | annotations.              |
++-----------+-----------------+---------------------------+
+| traceback | tb_frame        | frame object at this      |
+|           |                 | level                     |
++-----------+-----------------+---------------------------+
+|           | tb_lasti        | index of last attempted   |
+|           |                 | instruction in bytecode   |
++-----------+-----------------+---------------------------+
+|           | tb_lineno       | current line number in    |
+|           |                 | Python source code        |
++-----------+-----------------+---------------------------+
+|           | tb_next         | next inner traceback      |
+|           |                 | object (called by this    |
+|           |                 | level)                    |
++-----------+-----------------+---------------------------+
+| frame     | f_back          | next outer frame object   |
+|           |                 | (this frame's caller)     |
++-----------+-----------------+---------------------------+
+|           | f_builtins      | builtins namespace seen   |
+|           |                 | by this frame             |
++-----------+-----------------+---------------------------+
+|           | f_code          | code object being         |
+|           |                 | executed in this frame    |
++-----------+-----------------+---------------------------+
+|           | f_globals       | global namespace seen by  |
+|           |                 | this frame                |
++-----------+-----------------+---------------------------+
+|           | f_lasti         | index of last attempted   |
+|           |                 | instruction in bytecode   |
++-----------+-----------------+---------------------------+
+|           | f_lineno        | current line number in    |
+|           |                 | Python source code        |
++-----------+-----------------+---------------------------+
+|           | f_locals        | local namespace seen by   |
+|           |                 | this frame                |
++-----------+-----------------+---------------------------+
+|           | f_restricted    | 0 or 1 if frame is in     |
+|           |                 | restricted execution mode |
++-----------+-----------------+---------------------------+
+|           | f_trace         | tracing function for this |
+|           |                 | frame, or ``None``        |
++-----------+-----------------+---------------------------+
+| code      | co_argcount     | number of arguments (not  |
+|           |                 | including \* or \*\*      |
+|           |                 | args)                     |
++-----------+-----------------+---------------------------+
+|           | co_code         | string of raw compiled    |
+|           |                 | bytecode                  |
++-----------+-----------------+---------------------------+
+|           | co_consts       | tuple of constants used   |
+|           |                 | in the bytecode           |
++-----------+-----------------+---------------------------+
+|           | co_filename     | name of file in which     |
+|           |                 | this code object was      |
+|           |                 | created                   |
++-----------+-----------------+---------------------------+
+|           | co_firstlineno  | number of first line in   |
+|           |                 | Python source code        |
++-----------+-----------------+---------------------------+
+|           | co_flags        | bitmap: 1=optimized ``|`` |
+|           |                 | 2=newlocals ``|`` 4=\*arg |
+|           |                 | ``|`` 8=\*\*arg           |
++-----------+-----------------+---------------------------+
+|           | co_lnotab       | encoded mapping of line   |
+|           |                 | numbers to bytecode       |
+|           |                 | indices                   |
++-----------+-----------------+---------------------------+
+|           | co_name         | name with which this code |
+|           |                 | object was defined        |
++-----------+-----------------+---------------------------+
+|           | co_names        | tuple of names of local   |
+|           |                 | variables                 |
++-----------+-----------------+---------------------------+
+|           | co_nlocals      | number of local variables |
++-----------+-----------------+---------------------------+
+|           | co_stacksize    | virtual machine stack     |
+|           |                 | space required            |
++-----------+-----------------+---------------------------+
+|           | co_varnames     | tuple of names of         |
+|           |                 | arguments and local       |
+|           |                 | variables                 |
++-----------+-----------------+---------------------------+
+| generator | __name__        | name                      |
++-----------+-----------------+---------------------------+
+|           | __qualname__    | qualified name            |
++-----------+-----------------+---------------------------+
+|           | gi_frame        | frame                     |
++-----------+-----------------+---------------------------+
+|           | gi_running      | is the generator running? |
++-----------+-----------------+---------------------------+
+|           | gi_code         | code                      |
++-----------+-----------------+---------------------------+
+|           | gi_yieldfrom    | object being iterated by  |
+|           |                 | ``yield from``, or        |
+|           |                 | ``None``                  |
++-----------+-----------------+---------------------------+
+| coroutine | __name__        | name                      |
++-----------+-----------------+---------------------------+
+|           | __qualname__    | qualified name            |
++-----------+-----------------+---------------------------+
+|           | cr_await        | object being awaited on,  |
+|           |                 | or ``None``               |
++-----------+-----------------+---------------------------+
+|           | cr_frame        | frame                     |
++-----------+-----------------+---------------------------+
+|           | cr_running      | is the coroutine running? |
++-----------+-----------------+---------------------------+
+|           | cr_code         | code                      |
++-----------+-----------------+---------------------------+
+| builtin   | __doc__         | documentation string      |
++-----------+-----------------+---------------------------+
+|           | __name__        | original name of this     |
+|           |                 | function or method        |
++-----------+-----------------+---------------------------+
+|           | __qualname__    | qualified name            |
++-----------+-----------------+---------------------------+
+|           | __self__        | instance to which a       |
+|           |                 | method is bound, or       |
+|           |                 | ``None``                  |
++-----------+-----------------+---------------------------+
 
 .. versionchanged:: 3.5
 
@@ -226,10 +221,6 @@ attributes:
    The ``__name__`` attribute of generators is now set from the function
    name, instead of the code name, and it can now be modified.
 
-.. versionchanged:: 3.6
-
-   Add ``__definition_order__`` to classes.
-
 
 .. function:: getmembers(object[, predicate])
 
diff --git a/Doc/library/types.rst b/Doc/library/types.rst
index 5eb84c1..898b95a 100644
--- a/Doc/library/types.rst
+++ b/Doc/library/types.rst
@@ -53,19 +53,13 @@ Dynamic Type Creation
    in *kwds* argument with any ``'metaclass'`` entry removed. If no *kwds*
    argument is passed in, this will be an empty dict.
 
-   .. impl-detail::
-
-      CPython uses :class:`collections.OrderedDict` for the default
-      namespace.
-
    .. versionadded:: 3.3
 
    .. versionchanged:: 3.6
 
       The default value for the ``namespace`` element of the returned
-      tuple has changed from :func:`dict`.  Now an insertion-order-
-      preserving mapping is used when the metaclass does not have a
-      ``__prepare__`` method,
+      tuple has changed.  Now an insertion-order-preserving mapping is
+      used when the metaclass does not have a ``__prepare__`` method,
 
 .. seealso::
 
diff --git a/Doc/reference/compound_stmts.rst b/Doc/reference/compound_stmts.rst
index ffdeae0..4fc6af0 100644
--- a/Doc/reference/compound_stmts.rst
+++ b/Doc/reference/compound_stmts.rst
@@ -634,15 +634,9 @@ dictionary.  The class name is bound to this class object in the original local
 namespace.
 
 The order in which attributes are defined in the class body is preserved
-in the ``__definition_order__`` attribute on the new class.  If that order
-is not known then the attribute is set to :const:`None`.  The class body
-may include a ``__definition_order__`` attribute.  In that case it is used
-directly.  The value must be a tuple of identifiers or ``None``, otherwise
-:exc:`TypeError` will be raised when the class statement is executed.
-
-.. versionchanged:: 3.6
-
-   Add ``__definition_order__`` to classes.
+in the new class's ``__dict__``.  Note that this is reliable only right
+after the class is created and only for classes that were defined using
+the definition syntax.
 
 Class creation can be customized heavily using :ref:`metaclasses <metaclasses>`.
 
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index 00785ed..a075503 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -1752,13 +1752,6 @@ additional keyword arguments, if any, come from the class definition).
 If the metaclass has no ``__prepare__`` attribute, then the class namespace
 is initialised as an empty ordered mapping.
 
-.. impl-detail::
-
-   In CPython the default is :class:`collections.OrderedDict`.
-
-.. versionchanged:: 3.6
-   Defaults to :class:`collections.OrderedDict` instead of :func:`dict`.
-
 .. seealso::
 
    :pep:`3115` - Metaclasses in Python 3000