`in` operation on `tuple` of `Literal` doesn't narrow type

[Keymasterer44]

Describe the Bug

from typing import *

SeverityLevel = Literal["light", "minor", "major"]
SEVERITY_LEVELS = cast(tuple[SeverityLevel, ...], get_args(SeverityLevel))

severity_level_str: str = "light"
if severity_level_str in SEVERITY_LEVELS:
    reveal_type(severity_level_str)

When severity_level_str is checked to be in SEVERITY_LEVELS, this should narrow the type to SeverityLevel since only SeverityLevels are present in the tuple. In practice however, Pyrefly doesn't perform any narrowing based on the condition, severity_level_str is still just a str instead of SeverityLevel within the condition body.

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeS4ATrgLYAEALqcROgOZ0Q3G6UN0AqADroRAZRgA3GJQhMAMlJhQ6AXjry5M1FADaQkFAhsAFgwMAaOgZqtel6yBqoAVvZABdcQFEAat4AlAEkAFQBNAH15P295MTU6AGNUOAYACgYAV2JYXQlpWQUlKCtCMo8rNhgGCNRKNjg0-Jk5UkVpKABKTpEROCVC0gjYDojUykQ6cYSDI1NzEBEIMCmB1uHisYZKTnQ6MRjg8KiYuMQROku6SiUdCKZiGDT%2BgvWR5S3KHvQQCxAyG5gKCkQgMWhQCgAYjoAAVSIDgVMMDgCElcOhIGxMpRUAwIOjCCJoRIYHQzAxiHBEAB6akAmBAkG8NjUmDoamYXCJODUxLozHY3H49l0MC8OioSSoaCobCwNEY4yCvHoui4Ygq9BwQnoMgMEzogC0BTgwpmIAAzIQAIwAJgMIl0MmolDgXnQmXQXB4fBgmENmAgN0SeOkCQA5MZ0LwYOGRNGGIabgBHTJBv2GgDWMFIhtQiUS8DgEYA7nV0HGfgBfP750MwABi0BgFDQWDwRDIICrQA

(Only applicable for extension issues) IDE Information

No response

[yangdanny97]

Probably need to handle when the RHS is some iterable of literal types here:

pyrefly/pyrefly/lib/alt/narrow.rs

Line 1088 in 1abb101

}

We handle key membership in mapping and typeddicts already