Simplifications

 - Use range instead of Range in AsSeenFromMap#apply. We needed Range
   before because we did an incorrect variance computation for NamedTypes.

 - Refine derivedSelect

Author: odersky

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

@@ -40,7 +40,7 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
           case pre: SuperType => toPrefix(pre.thistpe, cls, thiscls)
           case _ =>
             if (thiscls.derivesFrom(cls) && pre.baseTypeRef(thiscls).exists)
-              if (variance <= 0 && !isLegalPrefix(pre)) Range(pre.bottomType, pre)
+              if (variance <= 0 && !isLegalPrefix(pre)) range(pre.bottomType, pre)
               else pre
             else if ((pre.termSymbol is Package) && !(thiscls is Package))
               toPrefix(pre.select(nme.PACKAGE), cls, thiscls)

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

@@ -3915,7 +3915,9 @@ object Types {
               // hence we can replace with U under all variances
               reapply(alias)
             case TypeBounds(lo, hi) =>
-              range(atVariance(-1)(reapply(lo)), atVariance(1)(reapply(hi)))
+              // If H#T = _ >: S <: U, then for any x in L..H, S <: x.T <: U,
+              // hence we can replace with S..U under all variances
+              range(atVariance(-variance)(reapply(lo)), reapply(hi))
             case info: SingletonType =>
               // if H#x: y.type, then for any x in L..H, x.type =:= y.type,
               // hence we can replace with y.type under all variances