Expand unions in order to solve generic overloads more precisely

[rouge8]

Describe the Bug

from typing import overload, TypeVar, NoReturn, reveal_type

T = TypeVar('T')

@overload
def not_none(val: None) -> NoReturn: ...

@overload
def not_none(val: T) -> T: ...

def not_none(val: T | None) -> T:
    if val is not None:
        return val
    else:
        raise AssertionError("It was None!")

def maybe_none() -> int | None:
    return 1

x = maybe_none()
reveal_type(x)

y = not_none(x)
reveal_type(y)

Python: 3.12

As of python/mypy#15846, mypy is able to infer that y is of type int, not int | None. It would be great if pyrefly could do the same!

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeS4ATrgLYAEALqcROgOZ0Q3G6UN24AbjEpRcqTABo6AFWYwAaqkrSAcrgBKMBgFdK6aZRjDUUAPpNiMADrpbMugF5Z8pZQAUAchmeAlLdsAASERMQlbTBgwOnRcBjNY9Bh3QVNEOnUk3zoAWgA%2BDM1tPXR0wnKA9GDhUXFMCKiYuITcJJS02Wz82TKKuyxG2PjE5NSodIcAH0Ks3IKZRFs6Zc5osc44Jv5MmEX0FYO6I119OjGllZgoOF2Lw6PUCBu6AEE4G74IVoBRSmoPawgACS-AA7qhNjsAISA-z9SLRGioUjYGAtNpdAqsfjTHZ7A7HEp0ACMlXwTjoSJRaJG7jhRhM5ksyXwcNspApQ3RLPpxhgpgs8ncpF8IEkIDIRjAUFIhAYtCgFAAxHQAAqkKUyuhoLB4ckAY1akDYelQDC%2B6EIthVAGUYDA6AALBgMYhwRAAeg9kqiMsIvDYHpg6A9mFw%2BrgHsN6GNpvNrQ9dDAvDoqFS0FQ2FgdGjscoZotAmI8fQcCt6DIDEdrRyNTghecgIAzIRiQAmQG2ADaIn%2BcAAurYdOguDw%2BDBMDlMBAjPrzcIKZ4IGxYkZPLYhjkjABHHQzic5ADWMFIOVQ%2Bv18E2zk84P06-QIAAvuLz-OYAAxaAwCg6nAEEhyCfIA

(Only applicable for extension issues) IDE Information

No response