AnyRef and AnyVal should be disjoint

[OlivierBlanvillain]

Looking at the documentation on AnyRef: "Class AnyRef is the root class of all reference types. All types except the value types descend from this class", I believe the following shouldn't compile:

case class Boo(i: Int) extends AnyVal                                 
val b: AnyRef = Boo(1)   

dottc accepts that code, but I think it should complain in the same way that scalac does:

scala> val a: AnyRef = Boo(1)                                                

                          ^
       error: type mismatch;
        found   : Boo
        required: AnyRef
       Note that Boo extends Any, not AnyRef.                                
       Such types can participate in value classes, but instances            
       cannot appear in singleton types or in reference comparisons.