Bug Report: TypeVar doesn't following narrowing in else branch and fails on returning narrowed types

[gsa-tspaere]

Describe the Bug

from typing import TypeVar, reveal_type

T = TypeVar("T", int, str, float)


def test(x: T) -> T:
    if isinstance(x, (int, float)):
        return x + 1
    else:
        return x.lower()


reveal_type(test(42))
reveal_type(test("HEY there"))

Python: 3.12

There are multiple problems, pyrefly fails to infer that x can only be a str in the else branch and it complains in the if branch, that an object of int | float cannot be returned to a type of T, even though it's literally a subset.

For pyright this works just fine

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeS4ATrgLYAEALqcROgOZ0Q3G6UN0AVZjABqqSgBo6lGADcYqKAH0mxGAB10mgXQC8g4WMoAKdSAFmprBlLgNJdMFFyoGASk2esMMI3gNjfERBNzoAWgA%2BQURNOjjOXwg4VjsMAGMYQKljayknF3c3GPR40ukYBgBXShL8OgBqOgBGWPiYKDgYYrL4mSqauiJnAHcYEw8tSZl5RRVhYwZ-YwAWACY3CemFZVVMxbtTEAAJAFEATUYACzGNEA2QCRAyGSdSQgZaKAoAYjoABVILygpDoaCweDqaVw6EgbGqrgg0MIml%2BAGUYDA6JcGAxiHBEAB6AnPHzAwi8NgEmDoAmYXBpOAEqEwiBwygI6EExy8OioWSoaCobCwOjM2HwhiIkq4YiS6FwZHoMgMS7QsLySjJaF6OhmADMhCaqzMmhAAF9Hqg0pL5AAxaAwChgnAEEjkM1AA

(Only applicable for extension issues) IDE Information

No response

[stroxler]

cc @rchen152 - this is tied to narrowing types that your current work might help fix, although it also looks like we're missing some handling of the negative case

[rchen152]

7497177 on its own doesn't seem to fix this; we probably need some additional work to make intersections with TypeVars work properly.