Pyre infers set-of-literals as set[str] rather than set[MyLiteral]

[jakewins]

Pyre Bug

Bug description

I expected the following script to pass type checking:

import typing as t

Foo = t.Literal["foo-1", "foo-2"]

FOO_1: Foo = "foo-1"
FOO_2: Foo = "foo-2"


def use_set_of_foos(v: set[Foo]):
    print(v)

# Typecheck fails here, because {FOO_1} is inferred to be set[str] rather than set[Foo]
use_set_of_foos({FOO_1})

Reproduction steps

See script above.

Expected behavior

I expected this to pass type checking

Logs
Please include any relevant logs here:

ƛ Found 1 type error!
repro.py:13:16 Incompatible parameter type [6]: In call `use_set_of_foos`, for 1st positional argument, expected `Set[Union[typing_extensions.Literal['foo-1'], typing_extensions.Literal['foo-2']]]` but got `Set[str]`.

rage.log

[kinto0]

Hi! Thanks for the report. We are currently tracking improvements to expression-level type inference which would solve your problem. I'll add this to the set of examples.