Question about how the Scala Compiler generates LabelDefs

Scala LabelDefs

$ cat test.scala
trait Foo[A] {
  final def bar(a:A):A = bar(a)
}

$ scalac -Xprint:tailcalls test.scala
[[syntax trees at end of                 tailcalls]] // test.scala
package <empty>#4 {
  abstract trait Foo#6[A#7308 >: Nothing#3704 <: Any#3703] extends Object#1785 {
    ...
    final def bar#7595(a#7606: A#7308): A#7308 = {
      <synthetic> val _$this#7844: Foo#6[A#7308] = Foo#6.this;
      _bar#7842(_$this#7844: Foo#6[A#7308], a#7606: A#7308){ // BEHAVIOR1: previously defined symbol (defined on the line above)
        _bar#7842(Foo#6.this, a#7606)
      }
    }
  }
}

$ cat test2.scala
object Test {
 def test[A](x: A) = x match {
   case _: Boolean => "bool"
 }
}

$ scalac -Xprint:tailcalls test2.scala -uniqid
[[syntax trees at end of                 tailcalls]] // test2.scala
package <empty>#4 {
  object Test#8 extends Object#1783 {
    def <init>#7591(): Test#7.type = {
      Test#8.super.<init>#5055();
      ()
    };
    def test#7592[A#7593 >: Nothing#3702 <: Any#3701](x#8780: A#7594): String#1867 = {
      case <synthetic> val x1#11851: A#7594 = x#8780;
      case4#11857(){
        if (x1#11851.isInstanceOf#5074[Boolean#1428]())
          {
            val x2#11854: A#7594 with Boolean#1428 = (x1#11851.asInstanceOf#5076[A#7594 with Boolean#1428](): A#7594 with Boolean#1428);
            matchEnd3#11855("bool")
          }
        else
          case5#11858()
      };
      case5#11858(){
        matchEnd3#11855(throw new MatchError#1179(x1#11851))
      };
      matchEnd3#11855(x#11856: String#1867){ // BEHAVIOR2: new symbol, not defined previously
        x#11856
      }
    }
  }
}

Look for BEHAVIOR1 and BEHAVIOR2 for a quick lookup.