I came across a compiler bug that involves a generics type with `scala.Int` . This can be one of the examples to show how they're handling primitive types internally. (Fixed in scala 2.10.1-RC1 by https://github.com/scala/scala/pull/1904 )

IntClassBug.scala

case class IntClassBug[A <: Int]() {
    def test(init:A) = {
          println("type=" + init.getClass)
    }
}

IntClassBug.scala_2_10_4.javap.txt

  public void test(A);
    Code:
       0: getstatic     #21;                // Field scala/Predef$.MODULE$:Lscala/Predef$;
       3: new           #23;                // class scala/collection/mutable/StringBuilder
       6: dup
       7: invokespecial #27;                // Method scala/collection/mutable/StringBuilder."<init>":()V
      10: ldc           #29;                // String type=
      12: invokevirtual #33;                // Method scala/collection/mutable/StringBuilder.append:(Ljava/lang/Object;)Lscala/collection/mutable/StringBuilder;
      15: iload_1
      16: invokestatic  #39;                // Method scala/runtime/BoxesRunTime.boxToInteger:(I)Ljava/lang/Integer;
      19: invokevirtual #43;                // Method java/lang/Object.getClass:()Ljava/lang/Class;
      22: invokevirtual #33;                // Method scala/collection/mutable/StringBuilder.append:(Ljava/lang/Object;)Lscala/collection/mutable/StringBuilder;
      25: invokevirtual #47;                // Method scala/collection/mutable/StringBuilder.toString:()Ljava/lang/String;
      28: invokevirtual #51;                // Method scala/Predef$.println:(Ljava/lang/Object;)V
      31: return

IntClassBug.scala_2_10_4.log

scala> new IntClassBug().test(3)
type=class java.lang.Integer

IntClassBug.scala_2_9_3.javap.txt

  public void test(A);
    Code:
       0: getstatic     #25;                // Field scala/Predef$.MODULE$:Lscala/Predef$;
       3: new           #27;                // class scala/collection/mutable/StringBuilder
       6: dup
       7: invokespecial #31;                // Method scala/collection/mutable/StringBuilder."<init>":()V
      10: ldc           #33;                // String type=
      12: invokevirtual #37;                // Method scala/collection/mutable/StringBuilder.append:(Ljava/lang/Object;)Lscala/collection/mutable/StringBuilder;
      15: iload_1
      16: invokevirtual #43;                // Method scala/Int.getClass:()Ljava/lang/Class;
      19: invokevirtual #37;                // Method scala/collection/mutable/StringBuilder.append:(Ljava/lang/Object;)Lscala/collection/mutable/StringBuilder;
      22: invokevirtual #47;                // Method scala/collection/mutable/StringBuilder.toString:()Ljava/lang/String;
      25: invokevirtual #51;                // Method scala/Predef$.println:(Ljava/lang/Object;)V
      28: return

IntClassBug.scala_2_9_3.log

scala> new IntClassBug().test(3)
java.lang.VerifyError: (class: IntClassBug, method: test signature: (I)V) Expecting to find object/array on stack
	at .<init>(<console>:8)
	at .<clinit>(<console>)
	at .<init>(<console>:11)
	at .<clinit>(<console>)
	at $print(<console>)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:704)
	at scala.tools.nsc.interpreter.IMain$Request$$anonfun$14.apply(IMain.scala:920)
	at scala.tools.nsc.interpreter.Line$$anonfun$1.apply$mcV$sp(Line.scala:43)
	at scala.tools.nsc.io.package$$anon$2.run(package.scala:25)
	at java.lang.Thread.run(Thread.java:745)