t5543.scala:3: error: not found: type T
  def this(x: T) { this() }
              ^
t5543.scala:11: error: not found: value x
   def this(a: Int, b: Int = x) {
                             ^
t5543.scala:18: error: not found: value x
  def this(a: Int = x) { this() }
                    ^
three errors found