`Self` not accepted when used with a `dataclass`

Using Self with a dataclass raises a type-var error even though Self is an acceptable type.

Suspect it may be the same as #18812.

To Reproduce

from __future__ import annotations
from dataclasses import dataclass
from typing import Self

type HasParent[N] = N | Node[N | HasParent[N]]


class Node[P = None]:
    def parent(self) -> P: ...  # type: ignore

@dataclass
class C[P: Node | None = Node | None](Node[P]):
    item: D[Self]

class D[P: HasParent[C] = C](Node[P]):
    pass

Changing to Self to the explicit class type (item: D[C]) is accepted. Similarly using Self in a regular class (e.g. below with __init__) does not raise any errors.

class C[P: Node | None = Node | None](Node[P]):
    def __init__(self, item: D[Self]):
        self.item = item

Expected Behavior

No errors.

Actual Behavior

error: Type argument "C[P]" of "D" must be a subtype of "HasParent[C[Node[None] | None]]"  [type-var]
error: Type argument "Self" of "D" must be a subtype of "HasParent[C[Node[None] | None]]"  [type-var]

Environment

• Mypy version used: 1.15.0
• Python version used: 13.2

Start by running the supplied reproduction with mypy 1.15.0, then compare the dataclass case with the regular-class variant and the explicit C type argument. Trace the existing handling of Self, dataclass fields, and generic type-variable bounds; done means the reproduction reports no errors and has a regression test.