IndexedSeqView throws ClassCastException on diff, intersect, etc.

[scabug]

scala> def iv = collection.mutable.IndexedSeq(1,2,3).view
iv: scala.collection.mutable.IndexedSeqView[Int,scala.collection.mutable.IndexedSeq[Int]]

scala> iv diff iv
java.lang.ClassCastException: scala.collection.SeqViewLike$$anon$1 cannot be cast to scala.collection.mutable.IndexedSeqView
  ... 32 elided

scala> iv intersect iv
java.lang.ClassCastException: scala.collection.SeqViewLike$$anon$1 cannot be cast to scala.collection.mutable.IndexedSeqView
  ... 32 elided

Problem is described in more detail in related issues #4190 and #6709. A sensible fix will cover them all. It's mostly SeqView's fault for .asInstanceOf[That]-ing without even checking cbf eq theCbfWeAreExpecting. (Relying on a bunch of manual overrides in IndexedSeqView is not a very good idea either.)

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-8640?orig=1
Reporter: @Ichoran
Affected Versions: 2.11.0
See #4190, #6709

[som-snytt]

Still on 2.12. As noted on gitter:

scala> ArrayBuffer(1,2,3,4,5,6,7).view.sliding(2).forall(_.nonEmpty)
java.lang.ClassCastException: scala.collection.SeqViewLike$$anon$1 cannot be cast to scala.collection.mutable.IndexedSeqView

[Ichoran]

Views are kinda wobbly in 2.12 anyway. If it's still in 2.13, that's a problem.

[dwijnand]

All ok in 2.13-landia

Welcome to Scala 2.13.0-RC2 (OpenJDK GraalVM CE 19.0.0, Java 1.8.0_212).
Type in expressions for evaluation. Or try :help.

scala> scala.collection.mutable.ArrayBuffer(1,2,3,4,5,6,7).view.sliding(2).forall(_.nonEmpty)
res0: Boolean = true