Uninitialized locals check

[lolpack]

def foo():
    x  # <- This should error
    x = 5

https://pyrefly.org/sandbox/?code=CYUwZgBGD20BQEoBcAoC6IA90GIIB4BaCAFQAsBLAZwirOgFcAbYCEAJ3enbQ2wF4IAViA

[yangdanny97]

This is partially supported for cases like x: int or x = 1; del x, but the specific example in the issue doesn't work yet so keeping this issue open