XXX Special case comparison with Any

Add the rule T <: Any for any *-Type T. This was not include fully before. We
did have the rule that T <: Any, if Any is in the base types of T. However,
it could be that the base type wrt Any does not exist. Example:

    Any#L <: Any

yielded false before, now yields true. This error manifested itself in i4031.scala.

With the new rule, we can drop again the special case in derivedSelect.

TODO: in the context of #4108, this seems questionable. Also, `Any#L` seems an
invalid type (even tho it is sound to consider it empty), and we'd probably not
want to accept it if the user writes it; here it is only OK because it's
introduced by avoidance. Or are user-written types checked elsewhere?

Author: odersky

compiler/src/dotty/tools/dotc/core/TypeComparer.scala

@@ -406,6 +406,7 @@ class TypeComparer(initctx: Context) extends ConstraintHandling {
             if (cls2 eq AnyKindClass) return true
             if (tp1.isRef(NothingClass)) return true
             if (tp1.isLambdaSub) return false
+            if (cls2 eq AnyClass) return true
               // Note: We would like to replace this by `if (tp1.hasHigherKind)`
               // but right now we cannot since some parts of the standard library rely on the
               // idiom that e.g. `List <: Any`. We have to bootstrap without scalac first.

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -4588,7 +4588,7 @@ object Types {
           forwarded.orElse(
             range(super.derivedSelect(tp, preLo).loBound, super.derivedSelect(tp, preHi).hiBound))
         case _ =>
-          if (pre == defn.AnyType) pre else super.derivedSelect(tp, pre) match {
+          super.derivedSelect(tp, pre) match {
             case TypeBounds(lo, hi) => range(lo, hi)
             case tp => tp
           }