To brace or not to brace: case statement block

Question

I am asking a specific question here (not an opinion): is there any scala style guide recommendation for the following "case o:" addressing whether the (optional) use of braces were to be avoided or if either with/without were both acceptable:

 def mycase(x : Int) = {
      x match {
      case 0 =>
        println("zero")
        println("blah zero")
      case 1 =>
        println("one")
      }

I was not initially convinced it would even work (thought it might do a fall through): but it does the correct breakout:

scala> mycase(0)
zero
blah zero

I specifically want to know if there were a canonical answer on this (not "I prefer" , etc.). E.g. for java, Sun had stated long ago that placing the initial curly brace for a method may happen either on same or next line - both are acceptable. is there such a clear answer in this case?

UPDATE An answer provided below by @acjay provides a link to the style guide. Inside here is a specific blurb.

from http://docs.scala-lang.org/style/control-structures.html#curlybraces

case - Omit braces if the case expression fits on a single line. Otherwise, use curly braces for clarity (even though they are not required by the parser).

Answer 1

The Scala's style guide about this http://docs.scala-lang.org/style/control-structures.html#curly-braces seems changed, where it says

case - Always omit braces in case clauses.

Actually, when editing in IntelliJ, it will remind user of unnecessary braces around case block.

Thus, to avoid introducing further confusion to users, please make a correction to the accepted answer :)

Answer 2

The Scala Documentation Style Guide says:

case - Omit braces if the case expression fits on a single line. Otherwise, use curly braces for clarity (even though they are not required by the parser).

Therefore, the correct format is:

def mycase(x : Int) = x match {
  case 0 => {
    println("zero")
    println("blah zero")
  }
  case 1 => println("one")
}

Separate from the question, but with pertinence to the example given, the declarations section of the style guide mentions the preferred formatting for the match as such:

Methods which contain a single match expression should be declared in the following way:

def sum(ls: List[Int]): Int = ls match {
  case hd :: tail => hd + sum(tail)
  case Nil => 0
}