# Release 4.9.0 (December 9, 2023)This feature release adds `typing_extensions.ReadOnly`, as specifiedby PEP 705, and makes various other improvements, especially to`@typing_extensions.deprecated()`.There are no changes since 4.9.0rc1.# Release 4.9.0rc1 (November 29, 2023)- Add support for PEP 705, adding `typing_extensions.ReadOnly`. Patch  by Jelle Zijlstra.- All parameters on `NewType.__call__` are now positional-only. This means that  the signature of `typing_extensions.NewType.__call__` now exactly matches the  signature of `typing.NewType.__call__`. Patch by Alex Waygood.- Fix bug with using `@deprecated` on a mixin class. Inheriting from a  deprecated class now raises a `DeprecationWarning`. Patch by Jelle Zijlstra.- `@deprecated` now gives a better error message if you pass a non-`str`  argument to the `msg` parameter. Patch by Alex Waygood.- `@deprecated` is now implemented as a class for better introspectability.  Patch by Jelle Zijlstra.- Exclude `__match_args__` from `Protocol` members.  Backport ofpython/cpython#110683 by Nikita Sobolev.- When creating a `typing_extensions.NamedTuple` class, ensure `__set_name__`  is called on all objects that define `__set_name__` and exist in the values  of the `NamedTuple` class's class dictionary. Patch by Alex Waygood,  backportingpython/cpython#111876.- Improve the error message when trying to call `issubclass()` against a  `Protocol` that has non-method members. Patch by Alex Waygood (backportingpython/cpython#112344, by Randolph Scholz).

…-method members (python#112344)Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

…-method members (python#112344)Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>