Tweak to prefix printing

Don't leave out package prefixes under homogenizedView. We want to see
them to make sure they are inserted in the same way before and after pickling.

This discovered a problem in unpickler where package object prefixes were not
correctly inserted back. Test case is pickleAlias.scala.

Author: odersky

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -1015,11 +1015,20 @@ class TreeUnpickler(reader: TastyReader,
         }
       }
 
-      def completeSelect(name: Name, tpf: Type => NamedType): Select = {
+      def completeSelect(name: Name, sig: Signature): Select = {
         val localCtx =
           if (name == nme.CONSTRUCTOR) ctx.addMode(Mode.InSuperCall) else ctx
         val qual = readTerm()(localCtx)
-        ConstFold(untpd.Select(qual, name).withType(tpf(qual.tpe.widenIfUnstable)))
+        var pre = qual.tpe.widenIfUnstable
+        val denot = accessibleDenot(pre, name, sig)
+        val owner = denot.symbol.maybeOwner
+        if (owner.isPackageObject && pre.termSymbol.is(Package))
+          pre = pre.select(owner.sourceModule)
+        val tpe = name match {
+          case name: TypeName => TypeRef(pre, name, denot)
+          case name: TermName => TermRef(pre, name, denot)
+        }
+        ConstFold(untpd.Select(qual, name).withType(tpe))
       }
 
       def readQualId(): (untpd.Ident, TypeRef) = {
@@ -1041,15 +1050,13 @@ class TreeUnpickler(reader: TastyReader,
         case IDENTtpt =>
           untpd.Ident(readName().toTypeName).withType(readType())
         case SELECT =>
-          def readRest(name: TermName, sig: Signature): Tree =
-            completeSelect(name, pre => TermRef(pre, name, accessibleDenot(pre, name, sig)))
           readName() match {
-            case SignedName(name, sig) => readRest(name, sig)
-            case name => readRest(name, Signature.NotAMethod)
+            case SignedName(name, sig) => completeSelect(name, sig)
+            case name => completeSelect(name, Signature.NotAMethod)
           }
         case SELECTtpt =>
           val name = readName().toTypeName
-          completeSelect(name, pre => TypeRef(pre, name, accessibleDenot(pre, name, Signature.NotAMethod)))
+          completeSelect(name, Signature.NotAMethod)
         case QUALTHIS =>
           val (qual, tref) = readQualId()
           untpd.This(qual).withType(ThisType.raw(tref))

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -109,7 +109,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
         if (isOmittable(tp.cls)) return ""
       case tp @ TermRef(pre, _) =>
         val sym = tp.symbol
-        if (sym.isPackageObject) return toTextPrefix(pre)
+        if (sym.isPackageObject && !homogenizedView) return toTextPrefix(pre)
         if (isOmittable(sym)) return ""
       case _ =>
     }

tests/pos/pickleAlias.scala

@@ -0,0 +1,3 @@
+object Test {
+  throw new scala.Error()
+}