-Xprint:jvm

[[syntax trees at end of                       jvm]] // Param.scala
package <empty> {
  final class Param extends Object {
    <paramaccessor> private[this] val i: Int = _;
    <stable> <accessor> <paramaccessor> def i(): Int = Param.this.i;
    override <synthetic> def hashCode(): Int = Param.hashCode$extension(Param.this.i());
    override <synthetic> def equals(x$1: Object): Boolean = Param.equals$extension(Param.this.i(), x$1);
    def <init>(i: Int): Param = {
      Param.this.i = i;
      Param.super.<init>();
      ()
    }
  };
  object Param extends Object {
    final private[this] val ConstantA: Int = _;
    final <stable> <accessor> def ConstantA(): Int = Param.this.ConstantA;
    final private[this] val ConstantB: Int = _;
    final <stable> <accessor> def ConstantB(): Int = Param.this.ConstantB;
    final <synthetic> def hashCode$extension($this: Int): Int = scala.Int.box($this).hashCode();
    final <synthetic> def equals$extension($this: Int, x$1: Object): Boolean = {
  case <synthetic> val x1: Object = x$1;
  case5(){
    if (x1.$isInstanceOf[Param]())
      matchEnd4(true)
    else
      case6()
  };
  case6(){
    matchEnd4(false)
  };
  matchEnd4(x: Boolean){
    x
  }
}.&&({
      <synthetic> val Param$1: Int = x$1.$asInstanceOf[Param]().i();
      $this.==(Param$1)
    });
    def <init>(): Param.type = {
      Param.super.<init>();
      Param.this.ConstantA = -1;
      Param.this.ConstantB = 0;
      ()
    }
  };
  object Main extends Object {
    def foo(i: Int): Int = i;
    def <init>(): Main.type = {
      Main.super.<init>();
      Main.this.foo(Param.ConstantA());
      ()
    }
  }
}

Param.scala

class Param(val i: Int) extends AnyVal

object Param{
  final val ConstantA = new Param(-1)

  final val ConstantB = new Param(0)
}

object Main{
  def foo(i: Param) = i

  foo(Param.ConstantA)
}