- Add support for PEP 728, supporting the `closed` keyword argument and the
special `__extra_items__` key for TypedDict. Patch by Zixuan James Li.
- Add support for PEP 742, adding `typing_extensions.TypeIs`. Patch
by Jelle Zijlstra.
- Drop runtime error when a read-only `TypedDict` item overrides a mutable
one. Type checkers should still flag this as an error. Patch by Jelle
Zijlstra.
- Speedup `issubclass()` checks against simple runtime-checkable protocols by
around 6% (backporting https://github.com/python/cpython/pull/112717, by Alex
Waygood).
- Fix a regression in the implementation of protocols where `typing.Protocol`
classes that were not marked as `runtime_checkable` would be unnecessarily
introspected, potentially causing exceptions to be raised if the protocol had
problematic members. Patch by Alex Waygood, backporting
https://github.com/python/cpython/pull/113401.