Dataclasses with Dataclass-Dict-Keys fail in asdict

[dan-fritchman]

Checks

• I added a descriptive title to this issue
• I have searched (google, github) for similar issues and couldn't find anything
• I have read and followed the docs and still think this is a bug

Bug

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.7.3
            pydantic compiled: True
                 install path: /Users/dan/miniconda3/envs/py38/lib/python3.8/site-packages/pydantic
               python version: 3.8.5 (default, Aug  5 2020, 03:39:04)  [Clang 10.0.0 ]
                     platform: macOS-10.16-x86_64-i386-64bit
     optional deps. installed: ['typing-extensions']

Thanks for all of your work on pydantic - it has been immensely valuable.

Bug report for dataclasses including Dict with other dataclasses as keys, failing to run dataclasses.asdict.

from pydantic.dataclasses import dataclass
from dataclasses import asdict
from typing import Dict

@dataclass(eq=True, frozen=True)
class A:
  a: str

@dataclass(eq=True, frozen=True)
class B:
  b: Dict[A, str]

asdict(B({A("x"):"y"}))

Yields:

Traceback (most recent call last):
  File "pydantic_asdict_demo.py", line 14, in <module>
    asdict(B({A("x"):"y"}))
  File "/Users/dan/miniconda3/envs/py38/lib/python3.8/dataclasses.py", line 1073, in asdict
    return _asdict_inner(obj, dict_factory)
  File "/Users/dan/miniconda3/envs/py38/lib/python3.8/dataclasses.py", line 1080, in _asdict_inner
    value = _asdict_inner(getattr(obj, f.name), dict_factory)
  File "/Users/dan/miniconda3/envs/py38/lib/python3.8/dataclasses.py", line 1110, in _asdict_inner
    return type(obj)((_asdict_inner(k, dict_factory),
TypeError: unhashable type: 'dict'

[dan-fritchman]

Looking some more, standard-library dataclasses fail the same way.

I can close if the expectation is that pydantic.dataclasses have parity with those.

[PrettyWood]

Hi @dan-fritchman
Indeed the behaviour is the same as stdlib dataclass and the error is actually "expected"
Happy new year!