Error on nested types

[kitschen]

In Python 3.7, type enforcing creates an error with the example code below. Given that this is valid Python, I would expect that this runs (even if the inner str type cannot be checked)

from dataclasses import dataclass
from typing import List, Optional
from unittest import TestCase

from enforce_typing import enforce_types


@enforce_types
@dataclass(frozen=True)
class Person:
    name: str
    siblings: Optional[List[str]]  # can be None or a List of strings


class TestPerson(TestCase):
    def test_creation(self):
        siblings = ["Bob", "Clair", ]
        p = Person(name="Alice", siblings=siblings) # fails here
        self.assertEqual("Alice", p.name)
        self.assertEqual(siblings, p.siblings)

This fails with TypeError: Subscripted generics cannot be used with class and instance checks Running on Python 3.7 with dataclasses 0.6 and enforce-typing 1.0.0.post1