Imported From: https://issues.scala-lang.org/browse/SI-1754?orig=1
Reporter: @paulp

@odersky said:
This would be possible only if we special case asInstanceOf, and I don't think we should do that.

@paulp said:
That's fine. I ask because I couldn't figure out what ticket #109 was trying to report, and it used asInstanceOf that way:

    def complete(sym : global.Symbol) = {
      Console.println("completing " + sym)
      typeParser.parseType(sym.asInstanceOf)
    }

@paulp said:
OK, it took me 2.5 years but I have to reopen this (reminded of it by #4871.) Why would this imply special casing asInstanceOf? As far as I can see it's the opposite: asInstanceOf is being given special status by not having to act the way everything else does.

Easily summarized:

scala> class Bip { def empty[T: Manifest, CC[_]] = { println(manifest[T]) ; null.asInstanceOf[CC[T]] } }
defined class Bip

scala> val x: Set[Int] = (new Bip).empty
Int
x: Set[Int] = null

scala> val x: Set[Int] = (new Bip).asInstanceOf
java.lang.ClassCastException: Bip cannot be cast to scala.runtime.Nothing$

Upon what basis should it infer Set[Int] when given nothing to go upon but the expected type, but in the same situation asInstanceOf should infer Nothing?

@paulp said:
I'm still not quite sure, but I lack sufficient curiosity to prolong.