Invalid type inference for generic typed dicts

[rnv812]

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

[sterliakov]

TypedDict's .get is handled by a built-in plugin, and plugin hooks are not invoked correctly for TypeVar types bound to smth interesting. The fullname passed to the hook is a garbled fallback like "get of Mapping".