哪些Scala方法返回null而不是Option，为什么？

Option

$ scala
Welcome to Scala version 2.9.0.1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_24).
Type in expressions to have them evaluated.
Type :help for more information.

scala> (<foo/>).scope.getURI(\"something\")
res0: String = null

String

Option[URI]

scala> val number = \"\"\"(\\d+)(\\.\\d+)?\"\"\".r // matches digits optionally followed by a . and more digits
number: scala.util.matching.Regex = (\\d+)(\\.\\d+)?
scala> \"12\" match {
     |   case number(intPart, decimalPart) => (intPart, decimalPart)
     | }
res0: (String, String) = (12,null)

Option[String]

Option[String]

null