Swift延迟声明放置

Question

在给定范围的上下文中包含defer语句的位置是否重要？这些都是一样的吗？

//1
{
    openFile();

    guard let x=y else {
        return
    }

    defer {
        closeFile()
    }
}

//2
{
    openFile();

    defer {
        closeFile()
    }

    guard let x=y else {
        return
    }
}

//3
{
    defer {
        closeFile()
    }

    openFile();

    guard let x=y else {
        return
    }
}