__post_init__() causes INTERNAL ERROR

[HongchengFan]

Crash Report

When I code with def __post_init__(), mypy reports INTERNAL ERROR.

To Reproduce

Here is a minimal code snippet to reproduce the crash:

def __post_init__(self):
  self._a = a

Print the code in the file.py and execute mypy file.py.

Traceback

file.py:2: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 1.5.1
Traceback (most recent call last):
  File "mypy/checker.py", line 584, in accept
  File "mypy/nodes.py", line 788, in accept
  File "mypy/checker.py", line 969, in visit_func_def
  File "mypy/checker.py", line 973, in _visit_func_def
  File "mypy/checker.py", line 1056, in check_func_item
  File "mypy/plugins/dataclasses.py", line 1092, in is_processed_dataclass
AttributeError: attribute 'metadata' of 'TypeInfo' undefined
file.py:2: : note: use --pdb to drop into pdb

Your Environment

• Mypy version used:1.5.1
• Mypy command-line flags: mypy file.py --show-traceback
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.9.0
• Operating system and version: Ubuntu 20.04.6 LTS

[AlexWaygood]

Looks like this is a recent regression. The code doesn't cause mypy to crash using mypy 1.4.1: https://mypy-play.net/?mypy=1.4.1&python=3.11&gist=ca0d08947e4e0659f5b8d4d794752422

But does with mypy 1.5.0 or mypy 1.5.1: https://mypy-play.net/?mypy=1.5.1&python=3.11&gist=4d266591df6934e48c26bc0f3fa61634