Erasure incorrectly rewrites isInstanceOf[X & Y] as isInstanceOf[X]

It should be rewritten as `isInstanceOf[X] && isInstanceOf[Y]` of course.
Test case that should run without asserting:
```scala
trait X
trait Y

object Test {
  def main(args: Array[String]): Unit = {
    val x: Any = new X {}
    assert(!x.isInstanceOf[X & Y])
  }
}
```