Initial Checks

• I confirm that I'm using Pydantic V2

Description

In v2.6.3 I had lines of code that rightfully needed type checking or mypy ignores for union-attr since the fields were typed like <type> | None. However, after I upgraded to v2.6.4 mypy is now telling me many of these type ignores are no longer necessary even though I didn't change my code at all. It seems to only be happening for classes that inherit from another model as you can see from my example. Anything that is just a BaseModel class seems to still require the type checking. I imagine its probably related to the change in this PR?

Example Code

from pydantic import BaseModel class Foo(BaseModel): id: int | None class Bar(BaseModel): foo: Foo | None class Baz(Bar): name: str b = Bar(foo={"id": 1}) z = Baz(foo={"id": 1}, name="test") assert z.foo.id == 1 # needed an ignore before assert b.foo.id == 1 # type: ignore[union-attr]

Python, Pydantic & OS Version

pydantic version: 2.6.4 pydantic-core version: 2.16.3 pydantic-core build: profile=release pgo=false install path: /fn/lib/venv/lib/python3.11/site-packages/pydantic python version: 3.11.8 (main, Mar 10 2024, 01:11:42) [GCC 10.2.1 20210110] platform: Linux-6.5.13-orbstack-00122-g57b8027e2387-aarch64-with-glibc2.31 related packages: typing_extensions-4.9.0 commit: unknown