[feat] variable directly called in binary expression is not grounded

[ValKmjolnir]

pub fn getParentByLevel(self, level: int) -> Self {
    if (level = 1) {
        return self.getParent()
    }

    let (p = self.getParent().getParentByLevel(level - 1)) {
    //                                         ^^^^^ level is not bound in this expression,
    //                                               `level - 1` is in fact a filter condition
        return p
    }
}

[xiexie]

lgtm