Csharp 在 out 参数中使用未分配的局部变量

我对C#给出"使用未分配的局部变量"编译错误有问题.我错过了什么？

// returns generic result of a function with error message 
// why the function failed
public class Result
{
    public bool isSuccess = true;
    public string errorMessage = string.Empty;

    public static implicit operator bool(Result r)
    {
        return r.isSuccess;
    }

    public static Result operator &(Result a, Result b)
    {
        return !a.isSuccess ? a : b;
    }

    public static Result operator |(Result a, Result b)
    {
        if (a.isSuccess)
        {
            return a;
        }
        if (b.isSuccess)
        {
            return b;
        }
        return new Result
        {
            isSuccess = false,
            errorMessage = $"{a.errorMessage}\nOut{b.errorMessage}"
        };
    }

    public static bool operator false(Result a)
    {
        return !a.isSuccess;
    }

    public static bool operator true(Result a)
    {
        return a.isSuccess;
    }
}

static Result Func1(int nIn, out int nOut)
{
    nOut = nIn + 1;
    return new Result();
}

private static void Main(string[] args)
{
    var resultA =
        Func1(0, out var a1) &&
        Func1(a1, out var a2); // compiles fine

    var resultB =
        Func1(0, out var b1) &&
        Func1(b1, out var b2) &&
        Func1(b2, out var b3); // Use of unassigned local variable 'b2'
}