Dataclass inheritance breakes ForwardRef

[Tishka17]

Bug report

Bug description:

If we have two classes split into two files with ForwardRefs, then you cannot get hints on __init__ method of child

parent.py:

from __future__ import annotations  # <--- this triggers the problem

from dataclasses import dataclass


class LocalDep:
    pass


@dataclass
class Parent:
    dep1: LocalDep

child.py

from dataclasses import dataclass
from typing import get_type_hints

from parent import Parent


@dataclass
class Child(Parent):
    pass

print(get_type_hints(Child))
print(get_type_hints(Child.__init__))

I've expected to have two last lines printing the same
Actually, first print gives a correct output, but the second call raises an error

Traceback (most recent call last):
  File "/home/tishka17/src/dishka/tmp/dtc/child.py", line 16, in <module>
    print(get_type_hints(Child.__init__))
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/typing.py", line 2414, in get_type_hints
    hints[name] = _eval_type(value, globalns, localns)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/typing.py", line 395, in _eval_type
    return t._evaluate(globalns, localns, recursive_guard)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/typing.py", line 905, in _evaluate
    eval(self.__forward_code__, globalns, localns),
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<string>", line 1, in <module>
NameError: name 'LocalDep' is not defined

As far as I udnerstood, we inside dataclass logic it copies __init__ method annotations and that leads to an error. We do not copy class attrs (fields), so hints are retrieved from parent class directly (get_type_hints knows about MRO)

CPython versions tested on:

3.11, 3.13, 3.14

Operating systems tested on:

Linux

[tuukkamustonen]

Also #89687

[Tishka17]

Ok, I'll close it, as it is duplicate