Invalid type inference for generic typed dicts

Bug Report

When we try to assert the type of an object obtained from get with default value from generic object bound to typed dict, then mypy shows next error:

error: Incompatible types in assignment (expression has type "object", variable has type "int")  [assignment]

To Reproduce

from typing import NotRequired, TypedDict, TypeVar


class A(TypedDict):
    i: NotRequired[int]


ParamsT = TypeVar('ParamsT', bound=A)


def foo(params: ParamsT) -> None:
    i: int = params.get('i', 0)


foo(A())

Gist: https://gist.github.com/mypy-play/effc3f0d297540be8ca1bad7b08c5902
Play: https://mypy-play.net/?mypy=latest&python=3.12&gist=effc3f0d297540be8ca1bad7b08c5902

Expected Behavior

It is expected that result of expression params.get('i', 0) would be of type int since typed dict attribute is annotated as <int> and the default value type is <int> as well.

Actual Behavior

Mypy reports that result of expression params.get('i', 0) has type <object>.

Your Environment

• Mypy version used: mypy 1.15.0 (compiled: yes)
• Python version used: 3.13

リポジトリのファイルもテストパスも指定されていません。まず、提供された Python の再現コードを mypy 1.15.0 で実行し、params.get('i', 0) に対して推論される型を確認してください。完了の条件は、この式が object ではなく int として推論され、汎用 TypedDict のケースに対するリグレッションカバレッジがあることです。