Add assert to find out whether code is redundant

Author: odersky

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

@@ -46,8 +46,11 @@ class Constructors extends MiniPhaseTransform with IdentityDenotTransformer { th
   private def markUsedPrivateSymbols(tree: RefTree)(implicit ctx: Context): Unit = {
 
     val sym = tree.symbol
-    def retain() =
+    def retain() = {
+      //println(i"retained: $sym")
+      //assert(i"$sym" != "value sf", ctx.owner.ownersIterator.toList)
       retainedPrivateVals.add(sym)
+    }
 
     if (sym.exists && sym.owner.isClass && mightBeDropped(sym)) {
       val owner = sym.owner.asClass
@@ -56,7 +59,8 @@ class Constructors extends MiniPhaseTransform with IdentityDenotTransformer { th
           case Ident(_) | Select(This(_), _) =>
             def inConstructor = {
               val method = ctx.owner.enclosingMethod
-              method.isPrimaryConstructor && ctx.owner.enclosingClass == owner
+              method.isPrimaryConstructor && ctx.owner.enclosingClass == owner// ||
+              // method.isGetter && !method.is(Lazy)
             }
             if (inConstructor && (sym.is(ParamAccessor) || seenPrivateVals.contains(sym))) {
               // used inside constructor, accessed on this,
@@ -79,8 +83,10 @@ class Constructors extends MiniPhaseTransform with IdentityDenotTransformer { th
   }
 
   override def transformValDef(tree: tpd.ValDef)(implicit ctx: Context, info: TransformerInfo): tpd.Tree = {
-    if (mightBeDropped(tree.symbol))
+    if (mightBeDropped(tree.symbol)) {
       (if (isWildcardStarArg(tree.rhs)) retainedPrivateVals else seenPrivateVals) += tree.symbol
+      assert(!isWildcardStarArg(tree.rhs))
+    }
     tree
   }
 
@@ -183,11 +189,13 @@ class Constructors extends MiniPhaseTransform with IdentityDenotTransformer { th
           case stat @ ValDef(name, tpt, _) if !stat.symbol.is(Lazy) && !stat.symbol.hasAnnotation(defn.ScalaStaticAnnot) =>
             val sym = stat.symbol
             if (isRetained(sym)) {
+              // println(i"$sym is retained")
               if (!stat.rhs.isEmpty && !isWildcardArg(stat.rhs))
                 constrStats += Assign(ref(sym), intoConstr(stat.rhs, sym)).withPos(stat.pos)
               clsStats += cpy.ValDef(stat)(rhs = EmptyTree)
             }
             else if (!stat.rhs.isEmpty) {
+              // println(i"$sym ${sym.flags} is not retained")
               dropped += sym
               sym.copySymDenotation(
                 initFlags = sym.flags &~ Private,