TypedDict attributes are always objects with TypeVar #15071

Bug Report

All attributes of TypedDict are "object", not the annotated type when using TypeVar

To Reproduce

class A(TypedDict):
    x: int
    y: str

class B(A):
    z: Dict[str, str]

T = TypeVar('T', bound=A)

def my_func(things: List[T]):
    for t in things:
        x_val: int = t['x'] # Incompatible types in assignment (expression has type "object", variable has type "int")
        y_val: str = t['y'] # Incompatible types in assignment (expression has type "object", variable has type "str")

my_things: List[B] = [
    {'x': 1, 'y': '2', 'z': {'foo': 'bar'}},
    {'x': 1, 'y': '2', 'z': {'foo': 'baz'}},
]
my_func(my_things)

Can do the same but with my_things: List[A] passed into the same function.
Doing something like z_val: Dict[str, str] = my_b_type['z'].get('foo') raises an error: "object" has no attribute "get"

Expected Behavior

It respects the type annotations and has access to attributes/methods of the type.

Actual Behavior

error: Incompatible types in assignment (expression has type "object", variable has type "int")
error: Incompatible types in assignment (expression has type "object", variable has type "str")
error: "object" has no attribute "get"

Your Environment

• Mypy version used: 0.812
• Mypy configuration options from mypy.ini (and other config files): n/a
• Python version used: 3.8.13