`get_type_hints` fails for `dataclass` in 3.14

[bfrandeen]

Bug report

Bug description:

This code works in 3.13, but fails in 3.14:

from dataclasses import dataclass
from typing import get_type_hints


@dataclass
class MyHintedClass:
    my_attr: int = 1

    def __init__(self):
        self.hints = get_type_hints(self)


my_class = MyHintedClass()
print(my_class.hints)

Failure in 3.14:

~\py\pybug: uv run --python=3.14 python main.py                                                                                                                                                                                                     
Traceback (most recent call last):
  File "C:\Users\bfrandeen\py\pybug\main.py", line 13, in <module>
    my_class = MyHintedClass()
  File "C:\Users\bfrandeen\py\pybug\main.py", line 10, in __init__
    self.hints = get_type_hints(self)
                 ~~~~~~~~~~~~~~^^^^^^
  File "C:\Users\bfrandeen\AppData\Roaming\uv\python\cpython-3.14.2-windows-x86_64-none\Lib\typing.py", line 2401, in get_type_hints
    hints = _lazy_annotationlib.get_annotations(obj, format=format)
  File "C:\Users\bfrandeen\AppData\Roaming\uv\python\cpython-3.14.2-windows-x86_64-none\Lib\annotationlib.py", line 996, in get_annotations
    raise TypeError(f"{obj!r} does not have annotations")
TypeError: MyHintedClass(my_attr=1) does not have annotations

Works in older versions:

~\py\pybug: uv run --python=3.13 python main.py
Using CPython 3.13.2
Removed virtual environment at: .venv
Creating virtual environment at: .venv
Installed 6 packages in 190ms
{'my_attr': <class 'int'>}

CPython versions tested on:

3.14, 3.13

Operating systems tested on:

Windows, Linux

[JelleZijlstra]

Previously get_type_hints() worked on instances by accident; we removed that support because it was not reliable and it was never documented. You should instead use e.g. get_type_hints(type(self)), which will work on all versions.

I'd be open to adding a note in the docs about this at https://docs.python.org/3.14/library/typing.html#typing.get_type_hints though.