Field initialization in dataclasses is not correct propagated

Bug Report

mypy should consider how the fields of a dataclass is initialized by the default constructor.

To Reproduce

from __future__ import annotations
from dataclasses import dataclass

@dataclass
class Node:
    item: int
    next: Node | None

p = Node(1, Node(2, None))

print(p.next.item)

Expected Behavior

mypy should consider the code valid.

Actual Behavior

It generates a error:

x.py:11: error: Item "None" of "Node | None" has no attribute "item"  [union-attr]
Found 1 error in 1 file (checked 1 source file)

Note that the following code is considered valid by mypy:

p = Node(1, None)
p.next = Node(2, Node)
print(p.next.item)

Your Environment

• Mypy version used: 1.8

Start with the x.py reproducer and inspect how mypy analyzes dataclass-generated constructors and field initialization. The work is done when the shown Node example is accepted without the union-attr error, while the existing None-handling behavior remains correct.