Bug report

Bug description:

This issue was originally reported in the beartype library (Ref: beartype/beartype#610), but investigation suggests it may stem from a change in Python’s annotationlib.ForwardRef implementation.

Starting with Python 3.14.1, deferred annotations (PEP 649) involving self-referential return type is raising: TypeError: unhashable type: 'cell' at decoration time. This worked correctly in Python 3.14.0 and the issue appears to persist in 3.14.2, suggesting a regression.

The error originates from annotationlib.ForwardRef.__hash__, which attempts to hash internal state containing non-hashable cell objects. Although observed via beartype, this may affects any downstream library that hashes ForwardRef objects. The following code seems to be raising the issue:
tuple(sorted(self.__cell__.items())) if isinstance(self.__cell__, dict) else self.__cell__,

	def __hash__(self):
	return hash((
	self.__forward_arg__,
	self.__forward_module__,
	id(self.__globals__), # dictionaries are not hashable, so hash by identity
	self.__forward_is_class__,
	tuple(sorted(self.__cell__.items())) if isinstance(self.__cell__, dict) else self.__cell__,
	self.__owner__,
	tuple(sorted(self.__extra_names__.items())) if self.__extra_names__ else None,
	))

Code:

#!pip install beartype==0.22.9
from beartype import beartype
class MyClass:
    @beartype
    def foo(self) -> MyClass:
        return MyClass()
print(MyClass().foo())

Observed behavior:

The program fails during decoration with the error: TypeError: unhashable type: 'cell'

File ".../beartype/_check/metadata/hint/hintsane.py", line 242, in __init__
    self._hash = hash((hint, hint_recursable_to_depth, typearg_to_hint))
File ".../python3.14/annotationlib.py", line 291, in __hash__
    return hash((..., tuple(sorted(self.__extra_names__.items()))))
TypeError: unhashable type: 'cell'

Inspection shows:

>>> self.__cell__
{'__classdict__': <cell at 0x...: dict object>}
>>> tuple(sorted(self.__cell__.items()))
(('__classdict__', <cell at 0x...>),)

Since cell objects are not hashable, this causes hash to fail.

Affected Versions:

Python 3.14.1 and 3.14.2
OS Tested on: MacOS

CPython versions tested on:

3.14

Operating systems tested on:

macOS