Subsequent `isinstance(cls, type)` and `issubclass(cls, upper_bound)` erase TypeVar information

[randolf-scholz]

Describe the Bug

This example fails:

class Foo: ...

def initialize[F: Foo](cls: type[F]) -> F:
    assert isinstance(cls, type)
    assert issubclass(cls, Foo)

    try: 
        inst = cls()
    except:
        raise

    return inst  # ❌️ E: Returned type `Foo` is not assignable to declared return type `F`

but if we uncomment either assert clause it succeeds. The root cause seems to be that the subsequence asserts narrow the type in a way that forgets the type variable:

reveal_type(cls)  # type[F]
assert isinstance(cls, type)
reveal_type(cls)  # type
assert issubclass(cls, Foo)
reveal_type(cls)  # type[Foo]

My expectation would be that neither assert changes the type, because

• type[F] & type should equal type[F] (n.b. type[F] & type[Any] would be another story...)
• type[F] & type[Foo] should equal type[F], as every F is a Foo.

Python: 3.14

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeS4ATrgLYAEALqcROgOZ0Q3G6UN2UYANxiooAfSbEYAHXRyAxlFRw4dAGK5ciOoT1y5mGGE7oIDCGIgAvGAG11OzbgC6ACiVwdU%2B%2BpcBKOgBaAD4NRDk6KIFhUQkfDyg4QLoAYkZmXxdI6JU4GD5OOFY4BgwFGES4ABoM6X8cqMERMUlMqpT0n0a6PIL%2BCFUAV2wlPKra5wb0aJiW%2BPbPTrrfLWz5GeiGSlIdHtmS-gBeOk83admYfAriBgjN2abUQdkN2cEGIcoZw6j0wBlyQDwf3QAKI6ABKME%2B3xgmBWdAABs4EUU6OhcPw8hA2OhUNhYIxcHQjGNBHCPl8Zj5EeoESBqiAhhYkiRyIgQOkAKrM8ykOhgIboBQWXDoOAGLDGfm8GioBjidBDGjYApufA6VgMQKhOilSj3d5Qyn8mQgABySpV%2BrowHwAF9TXJ6SAyIIwFBSIQGLQoBR0gAFUhuj26jA4AinUWQNhfOUQUWEOTpADKMBgdAAFgwGMQvAB6POu4wewi8Nh5mDoPOYXAKOB5hRR7GxkVV6WUXpCZ7KfHpxvoaMt%2BMzXC3YdwRPoMgMDOioIiSjFUV0E6mgDMhAAjAAmR3oEB2hmoYUQETqaAwChoLB4IhkA9AA

(Only applicable for extension issues) IDE Information

No response