abstract class WordExp extends Base {

  abstract class Label

  type _regexpT <: RegExp
  type _labelT <: Label

  case class Letter(a: _labelT) extends RegExp {
    final lazy val isNullable = false
    var pos = -1
  }

  case class Wildcard() extends RegExp {
    final lazy val isNullable = false
    var pos = -1
  }
}

[[syntax trees at end of cleanup]]// Scala source: WordExp.scala
package scala.util.regexp {
  abstract class WordExp extends scala.util.regexp.Base with ScalaObject {
    . . . 
    @serializable case class Wildcard extends scala.util.regexp.Base#RegExp with ScalaObject with Product {

      @volatile protected var bitmap$$0: Int = 0;

      final lazy private[this] var isNullable: Boolean = _; /*- it's a final field */

      final <stable> <accessor> lazy def isNullable(): Boolean = {
        if (Wildcard.this.bitmap$$0.&(1).==(0))
          {
            Wildcard.this.synchronized({
              if (Wildcard.this.bitmap$$0.&(1).==(0))
                {
                  Wildcard.this.isNullable = false; /*- yet it's written outside a constructor. 
                                                        The CLR doesn't like this. */
                  Wildcard.this.bitmap$$0 = Wildcard.this.bitmap$$0.|(1);
                  ()
                };
              scala.runtime.BoxedUnit.UNIT
            });
            ()
          };
        Wildcard.this.isNullable
      };
    . . .