为什么Scala的分号推论在这里失败？

package spoj

object Prime1 {
  def main(args: Array[String]) {
    def isPrime(n: Int) = (n != 1) && (2 to n/2 forall (n % _ != 0))
    val read = new java.util.Scanner(System.in)
    var nTests = read nextInt // [*]
    while(nTests > 0) {
      val (start,end) = (read nextInt,read nextInt)
      start to end filter(isPrime(_)) foreach println
      println
      nTests -= 1
    }
  }
}

我得到以下编译时错误：

PRIME1.scala:8: error: illegal start of simple expression
    while(nTests > 0) {
    ^
PRIME1.scala:14: error: block must end in result expression,not in definition
  }
  ^
two errors found

当我在文章末尾添加一个分号作为[*]时，该程序编译正常。任何人都可以解释为什么Scala的分号推论不能在特定的行上工作？