必须替换为：case 0 => result

可能与OP不相关，但我用这个答案作为例子，这个版本是有效的：

def power(base: Int, exp: Int): BigInt = {
    def _power(result: BigInt, exp: Int): BigInt = exp match {
        case 0 => 1
        case 1 => result
        case _ => _power(result*base, exp-1)
    }
    _power(base, exp)
}

更好的尾递归解决方案（堆栈安全）可能如下所示：

def power(base: Int, exp: Int): BigInt {

  @scala.annotation.tailrec
  def loop(x: BigInt, n: Long, kx: BigInt): BigInt = {
    if (n == 1) x * kx
    else {
      if (n % 2 == 0)
        loop(x * x, n / 2, kx)
      else
        loop(x, n - 1, x * kx) // O(log N) time complexity!
    }
  }

  if (n == 0) 1
  else {
    val pow = loop(base, Math.abs(exp.toLong), 1)
    if (n > 0) pow else 1 / pow
  }

}