Side effects incorrectly elided by Erasure's handling of Unit

[scabug]

next code:

object A {
  val init = println("hello")
}

object Main {
  def main(args: Array[String]) {
      val a = A.init
  }
}

produces no output, but "hello" is expected.
This behaviour was observed when trying code described here http://stackoverflow.com/questions/24221601/scala-object-initialization

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-8666?orig=1
Reporter: Maksym Besida (mbesida)
Affected Versions: 2.10.3
See #5304

[scabug]

@retronym said:
This relates to #5304, which shows other examples where the object initialization is elided.

This particular instance comes down to:

//src/compiler/scala/tools/nsc/transform/TypeAdaptingTransformer.scala
          case UnitClass  =>
            if (treeInfo isExprSafeToInline tree) REF(BoxedUnit_UNIT)
            else BLOCK(tree, REF(BoxedUnit_UNIT))

isExprSafeToInline is insufficient, we have to check whether the tree is safe to elide.

[SethTisue]

I added a reference from #5304 to here. closing