>>> @dataclass
... class C:
...   f: "C"
...
>>> c = C(None)
>>> c.f = c
>>> c
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 2, in __repr__
  File "<string>", line 2, in __repr__
  File "<string>", line 2, in __repr__
  [Previous line repeated 328 more times]
RecursionError: maximum recursion depth exceeded
>>>

It would be better to produce "C(f=...)".