用Groovy进行尾递归

>首先,我希望Stack Overflow失败.没问题.
>其次,我尝试尾部重用调用,将先前的算法从递归转换为迭代.它不起作用,但我不明白为什么.
>第三,我使用trampoline()方法并且按照我的预期正常工作.

def factorial

factorial = { BigInteger n ->
    if (n == 1) return 1
    n * factorial(n - 1)
}
factorial(1000)  // Stack Overflow

factorial = { Integer n,BigInteger acc = 1 ->
    if (n == 1) return acc
    factorial(n - 1,n * acc)
}
factorial(1000)  // Stack Overflow,why???

factorial = { Integer n,BigInteger acc = 1 ->
     if (n == 1) return acc
     factorial.trampoline(n - 1,n * acc)
}.trampoline()
factorial(1000)  // It works