Erasure doesn't insert all box\unbox corsions for ifs

[DarkDimius]

    def id[T](t: T) = t
    { if (x) id(one) else 0} + 1
    { if (x) new scala.util.Random()}.asInstanceOf[Runnable]

After erasure both those if's have different types of branches:

    { if (x) id(box(one)) else 0} + 1
    { if (x) new scala.util.Random() else ()}.asInstanceOf[Runnable]

In first example id should get unboxed,
In the second example () should get boxed.