Forward Reference Validation

[mlamby]

Thanks for creating this great library~

I have the following code that uses a forward reference per PEP484.

@dataclass_validate
@dataclass
class DC4:
    member1: str
    # member2 can be either a string or a DC4 instance
    member2: Union[str, "DC4"]

def test_forwardReference():
    DC4("Hello", "World")
    DC4("Hello", DC4("World", "Too"))

    # This should raise a validation error but doesn't
    with pytest.raises(TypeValidationError) as e:
        DC4("Hello", 1) 

At the moment I can set member2 to any value and no TypeValidationError is raised.

I suspect this is because the forward reference is not resolved by the dataclass library. If I print out the type of each field of DC4 I get the following:

member1: <class 'str'>
member2: typing.Union[str, ForwardRef('DC4')]

Is this a use case that you have considered?