Parsing failure [404]: f-string expression part cannot include a backslash

[0ri0n ☠]

Pyre Bug

Bug description
Using backslashes inside an f-string expression under Python 3.12 produces the following Pyre error:

Parsing failure [404]: f-string expression part cannot include a backslash

Reproduction steps

foo = ['1', '2', '3', '4']
print(f"{'\n'.join(foo)}")  # error for this line

Expected behavior
It should be able to parse the code and not produce an error as Python 3.12 supports backslashes in f-string expressions per PEP 701

I am using pyre-nightly PyPi package.

[Kyle Into]

adding this to a milestone for 3.12. it will take some time for us to support all the 3.12 features. that being said, typechecking just uses the CPython parser so we probably just need to update to a newer version.