None not being assigned to Union

[rllin]

packages
marshmallow==3.6.1
marshmallow-dataclass==7.6.0
marshmallow-enum==1.5.1
marshmallow-union==0.1.15

from typing import List, Union

from marshmallow_dataclass import dataclass

import dataclasses

noned = lambda: dataclasses.field(
    metadata=dict(
        required=False,
        missing=None,
        default=None,
    )
)

@dataclass
class Inner:
    inner_var: int

@dataclass
class Test:
    req: int = None
    var: Union[int, Inner, List[Inner]] = noned()

I get the following error trying to use the class

/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:1019: in dataclass
    return wrap(cls)
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:1011: in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:925: in _process_class
    _init_fn(flds,
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:502: in _init_fn
    raise TypeError(f'non-default argument {f.name!r} '
E   TypeError: non-default argument 'var' follows default argument

It seems like default and missing None are not being assigned properly?

[lovasoa]

Your type annotation is incorrect. A field of typeUnion[int, Inner, List[Inner]] cannot be None.

[rllin]

oh how come? the following is valid. am i missing something?

@dataclass
class Inner:
    inner_var: int = None

[lovasoa]

None is not an instance of int. You can use Optional[int] or Union[int, None]

See typing — Support for type hints — Python 3.8.3 documentation
https://docs.python.org/3/library/typing.html#typing.Optional