Use empty roots for tasty terms

Author: nicolasstucki

compiler/src/dotty/tools/dotc/core/quoted/PickledQuotes.scala

@@ -105,7 +105,7 @@ object PickledQuotes {
     }
 
     val unpickler = new TastyUnpickler(bytes, splices)
-    unpickler.enter(Set(ctx.owner))
+    unpickler.enter(Set.empty)
     val tree = unpickler.tree
 
     if (pickling ne noPrinter)

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

@@ -869,11 +869,12 @@ class TreeUnpickler(reader: TastyReader,
       nextByte == IMPORT || nextByte == PACKAGE
 
     def readTopLevel()(implicit ctx: Context): List[Tree] = {
-      @tailrec def read(acc: ListBuffer[Tree]): List[Tree] = nextByte match {
-        case IMPORT | PACKAGE =>
+      @tailrec def read(acc: ListBuffer[Tree]): List[Tree] = {
+        if (isTopLevel) {
           acc += readIndexedStat(NoSymbol)
           if (!isAtEnd) read(acc) else acc.toList
-        case _ => // top-level trees which are not imports or packages are not part of tree
+        }
+        else // top-level trees which are not imports or packages are not part of tree
           acc.toList
       }
       read(new ListBuffer[tpd.Tree])

compiler/src/dotty/tools/dotc/transform/Pickler.scala

@@ -94,7 +94,7 @@ class Pickler extends Phase {
     val unpicklers =
       for ((cls, pickler) <- picklers) yield {
         val unpickler = new DottyUnpickler(pickler.assembleParts())
-        unpickler.enter(roots = Set())
+        unpickler.enter(roots = Set.empty)
         cls -> unpickler
       }
     pickling.println("************* entered toplevel ***********")