from __future__ import annotations
import dataclasses as dcls
import inspect
import typing
import typing_extensions as typx
assert typing.ClassVar is typx.ClassVar
@dcls.dataclass
class Foo:
    y: int
    x: typing.ClassVar[ int ] = 1
print( "\n=== typing.ClassVar (ok) ===" )
print( 'anno', Foo.__init__.__annotations__ )
print( 'inspect', inspect.get_annotations( Foo.__init__, eval_str = True ) )
print( 'typing', typing.get_type_hints( Foo.__init__ ) )
print( 'typx', typx.get_type_hints( Foo.__init__ ) )
@dcls.dataclass
class Bar:
    y: int
    x: typx.ClassVar[ int ] = 1
print( "\n=== typing_extensions.ClassVar (breaks) ===" )
print( 'anno', Bar.__init__.__annotations__ )
print( 'inspect', inspect.get_annotations( Bar.__init__, eval_str = True ) )
print( 'typing', typing.get_type_hints( Bar.__init__ ) )
print( 'typx', typx.get_type_hints( Bar.__init__ ) )

=== typing.ClassVar (ok) ===
anno {'y': 'int', 'return': None}
inspect {'y': <class 'int'>, 'return': None}
typing {'y': <class 'int'>, 'return': <class 'NoneType'>}
typx {'y': <class 'int'>, 'return': <class 'NoneType'>}
=== typing_extensions.ClassVar (breaks) ===
anno {'y': 'int', 'x': 'typx.ClassVar[int]', 'return': None}
inspect {'y': <class 'int'>, 'x': typing.ClassVar[int], 'return': None}
Traceback (most recent call last):
  File "/home/me/src/somepkg/bugs/dcls-classvar-hints.py", line 38, in <module>
    print( 'typing', typing.get_type_hints( Bar.__init__ ) )
  File "/usr/lib/python3.10/typing.py", line 1871, in get_type_hints
    value = _eval_type(value, globalns, localns)
  File "/usr/lib/python3.10/typing.py", line 327, in _eval_type
    return t._evaluate(globalns, localns, recursive_guard)
  File "/usr/lib/python3.10/typing.py", line 693, in _evaluate
    type_ = _type_check(
  File "/usr/lib/python3.10/typing.py", line 167, in _type_check
    raise TypeError(f"{arg} is not valid as type argument")
TypeError: typing.ClassVar[int] is not valid as type argument