`reportPossiblyUnboundVariable` false negative on assignments to instance attribute

[DetachHead]

Code sample in basedpyright playground

class Foo:
    def __init__(self) -> None:
        if bool():
            a = 1
        a # "a" is possibly unbound  (reportPossiblyUnboundVariable)
        if bool():
            self.a = 1
        self.a # no error

[DetachHead]

maybe related?: #682