from typing import TypeVar

class A:
    pass
class B:
    b: int

T = TypeVar("T", bound=A | B)


def foo(x: T) -> T:
    if isinstance(x, A):
        reveal_type(x)      # N: Revealed type is "__main__.A"
    else:
        reveal_type(x)      # N: Revealed type is "T`-1"
        x.b                 # E: Item "A" of the upper bound "A | B" of type variable "T" has no attribute "b"
    return x

from typing import TypeVar

class A:
    pass
class B:
    b: int

T = TypeVar("T", bound=A | B)


def foo(x: T) -> T:
    if isinstance(x, A):
        reveal_type(x)      # N: Revealed type is "__main__.A"
    else:
        reveal_type(x)      # N: Revealed type is "T`-1"
        x.b                 # ok! Upper bound of T narrowed to B
    return x