# Release 4.9.0 (December 9, 2023)

This feature release adds `typing_extensions.ReadOnly`, as specified
by 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 of python/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,
  backporting python/cpython#111876.
- Improve the error message when trying to call `issubclass()` against a
  `Protocol` that has non-method members. Patch by Alex Waygood (backporting
  python/cpython#112344, by Randolph Scholz).

…protocols (python#110683)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>