fix #9179: generate dollarvalues for parameterized enums, use serialization proxy

Author: bishabosha

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -505,7 +505,7 @@ object desugar {
         val targ = refOfDef(tparam)
         def fullyApplied(tparam: Tree): Tree = tparam match {
           case TypeDef(_, LambdaTypeTree(tparams, body)) =>
-            AppliedTypeTree(targ, tparams.map(_ => TypeBoundsTree(EmptyTree, EmptyTree)))
+            AppliedTypeTree(targ, tparams.map(_ => WildcardTypeBoundsTree()))
           case TypeDef(_, rhs: DerivedTypeTree) =>
             fullyApplied(rhs.watched)
           case _ =>

compiler/src/dotty/tools/dotc/ast/DesugarEnums.scala

@@ -77,9 +77,9 @@ object DesugarEnums {
   private def valuesDot(name: PreName)(implicit src: SourceFile) =
     Select(Ident(nme.DOLLAR_VALUES), name.toTermName)
 
-  private def registerCall(using Context): List[Tree] =
-    if (enumClass.typeParams.nonEmpty) Nil
-    else Apply(valuesDot("register"), This(EmptyTypeIdent) :: Nil) :: Nil
+  private def registerCall(using Context): Tree =
+    val asRaw = TypeApply(Select(This(EmptyTypeIdent), nme.asInstanceOf_), rawRef(enumClass.typeRef) :: Nil) // safe to cast due to refchecks
+    Apply(valuesDot("register"), asRaw :: Nil)
 
   /**  The following lists of definitions for an enum type E:
    *
@@ -93,12 +93,14 @@ object DesugarEnums {
    *       }
    */
   private def enumScaffolding(using Context): List[Tree] = {
+    import dotty.tools.dotc.transform.SymUtils._
+    val rawEnumClassRef = rawRef(enumClass.typeRef)
+    extension (tpe: NamedType) def ofRawEnum = AppliedTypeTree(ref(tpe), rawEnumClassRef)
     val valuesDef =
-      DefDef(nme.values, Nil, Nil, TypeTree(defn.ArrayOf(enumClass.typeRef)), Select(valuesDot(nme.values), nme.toArray))
+      DefDef(nme.values, Nil, Nil, defn.ArrayType.ofRawEnum, Select(valuesDot(nme.values), nme.toArray))
         .withFlags(Synthetic)
     val privateValuesDef =
-      ValDef(nme.DOLLAR_VALUES, TypeTree(),
-        New(TypeTree(defn.EnumValuesClass.typeRef.appliedTo(enumClass.typeRef :: Nil)), ListOfNil))
+      ValDef(nme.DOLLAR_VALUES, TypeTree(), New(defn.EnumValuesClass.typeRef.ofRawEnum, ListOfNil))
         .withFlags(Private | Synthetic)
 
     val valuesOfExnMessage = Apply(
@@ -138,7 +140,7 @@ object DesugarEnums {
       parents = enumClassRef :: scalaRuntimeDot(tpnme.EnumValue) :: Nil,
       derived = Nil,
       self = EmptyValDef,
-      body = List(ordinalDef, toStringDef) ++ registerCall
+      body = ordinalDef :: toStringDef :: registerCall :: Nil
     ).withAttachment(ExtendsSingletonMirror, ()))
     DefDef(nme.DOLLAR_NEW, Nil,
         List(List(param(nme.ordinalDollar_, defn.IntType), param(nme.nameDollar, defn.StringType))),
@@ -254,7 +256,7 @@ object DesugarEnums {
     val minKind = if (kind < seenKind) kind else seenKind
     ctx.tree.pushAttachment(EnumCaseCount, (count + 1, minKind))
     val scaffolding =
-      if (enumClass.typeParams.nonEmpty || kind >= seenKind) Nil
+      if (kind >= seenKind) Nil
       else if (kind == CaseKind.Object) enumScaffolding
       else if (seenKind == CaseKind.Object) enumValueCreator :: Nil
       else enumScaffolding :+ enumValueCreator
@@ -288,8 +290,8 @@ object DesugarEnums {
       val toStringDef = toStringMethLit(name.toString)
       val impl1 = cpy.Template(impl)(
         parents = impl.parents :+ scalaRuntimeDot(tpnme.EnumValue),
-        body = List(ordinalDef, toStringDef) ++ registerCall)
-        .withAttachment(ExtendsSingletonMirror, ())
+        body = ordinalDef :: toStringDef :: registerCall :: Nil
+      ).withAttachment(ExtendsSingletonMirror, ())
       val vdef = ValDef(name, TypeTree(), New(impl1)).withMods(mods.withAddedFlags(EnumValue, span))
       flatTree(scaffolding ::: vdef :: Nil).withSpan(span)
     }

compiler/src/dotty/tools/dotc/ast/untpd.scala

@@ -150,6 +150,13 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
     override def isEmpty: Boolean = true
   }
 
+  def WildcardTypeBoundsTree()(using src: SourceFile): TypeBoundsTree = TypeBoundsTree(EmptyTree, EmptyTree, EmptyTree)
+  object WildcardTypeBoundsTree:
+    def unapply(tree: untpd.Tree): Boolean = tree match
+      case TypeBoundsTree(EmptyTree, EmptyTree, _) => true
+      case _ => false
+
+
   /** A block generated by the XML parser, only treated specially by
    *  `Positioned#checkPos` */
   class XMLBlock(stats: List[Tree], expr: Tree)(implicit @constructorOnly src: SourceFile) extends Block(stats, expr)
@@ -453,6 +460,10 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   def ref(tp: NamedType)(using Context): Tree =
     TypedSplice(tpd.ref(tp))
 
+  def rawRef(tp: NamedType)(using Context): Tree =
+    if tp.typeParams.isEmpty then ref(tp)
+    else AppliedTypeTree(ref(tp), tp.typeParams.map(_ => WildcardTypeBoundsTree()))
+
   def rootDot(name: Name)(implicit src: SourceFile): Select = Select(Ident(nme.ROOTPKG), name)
   def scalaDot(name: Name)(implicit src: SourceFile): Select = Select(rootDot(nme.scala), name)
   def scalaAnnotationDot(name: Name)(using SourceFile): Select = Select(scalaDot(nme.annotation), name)

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

@@ -651,6 +651,12 @@ class Definitions {
     @tu lazy val Enum_ordinal: Symbol = EnumClass.requiredMethod(nme.ordinal)
 
   @tu lazy val EnumValuesClass: ClassSymbol = requiredClass("scala.runtime.EnumValues")
+  @tu lazy val EnumValueClass: ClassSymbol = requiredClass("scala.runtime.EnumValue")
+
+  @tu lazy val EnumValueSerializationProxyClass: ClassSymbol = requiredClass("scala.runtime.EnumValueSerializationProxy")
+    @tu lazy val EnumValueSerializationProxyConstructor: TermSymbol =
+      EnumValueSerializationProxyClass.requiredMethod(nme.CONSTRUCTOR, List(ClassType(TypeBounds.empty)))
+
   @tu lazy val ProductClass: ClassSymbol = requiredClass("scala.Product")
     @tu lazy val Product_canEqual          : Symbol = ProductClass.requiredMethod(nme.canEqual_)
     @tu lazy val Product_productArity      : Symbol = ProductClass.requiredMethod(nme.productArity)

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1491,7 +1491,7 @@ object Parsers {
     }
 
     private def makeKindProjectorTypeDef(name: TypeName): TypeDef =
-      TypeDef(name, TypeBoundsTree(EmptyTree, EmptyTree)).withFlags(Param)
+      TypeDef(name, WildcardTypeBoundsTree()).withFlags(Param)
 
     /** Replaces kind-projector's `*` in a list of types arguments with synthetic names,
      *  returning the new argument list and the synthetic type definitions.

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

@@ -355,31 +355,58 @@ class SyntheticMembers(thisPhase: DenotTransformer) {
     symbolsToSynthesize.flatMap(syntheticDefIfMissing)
   }
 
+  private def hasWriteReplace(clazz: ClassSymbol)(using Context): Boolean =
+    clazz.membersNamed(nme.writeReplace)
+      .filterWithPredicate(s => s.signature == Signature(defn.AnyRefType, isJava = false))
+      .exists
+
+  private def writeReplaceDef(clazz: ClassSymbol)(using Context): TermSymbol =
+    newSymbol(clazz, nme.writeReplace, Method | Private | Synthetic,
+        MethodType(Nil, defn.AnyRefType), coord = clazz.coord).entered.asTerm
+
   /** If this is a serializable static object `Foo`, add the method:
    *
    *      private def writeReplace(): AnyRef =
    *        new scala.runtime.ModuleSerializationProxy(classOf[Foo.type])
    *
    *  unless an implementation already exists, otherwise do nothing.
    */
-  def serializableObjectMethod(clazz: ClassSymbol)(using Context): List[Tree] = {
-    def hasWriteReplace: Boolean =
-      clazz.membersNamed(nme.writeReplace)
-        .filterWithPredicate(s => s.signature == Signature(defn.AnyRefType, isJava = false))
-        .exists
-    if (clazz.is(Module) && clazz.isStatic && clazz.isSerializable && !hasWriteReplace) {
-      val writeReplace = newSymbol(clazz, nme.writeReplace, Method | Private | Synthetic,
-        MethodType(Nil, defn.AnyRefType), coord = clazz.coord).entered.asTerm
+  def serializableObjectMethod(clazz: ClassSymbol)(using Context): List[Tree] =
+    if clazz.is(Module) && clazz.isStatic && clazz.isSerializable && !hasWriteReplace(clazz) then
       List(
-        DefDef(writeReplace,
+        DefDef(writeReplaceDef(clazz),
           _ => New(defn.ModuleSerializationProxyClass.typeRef,
                    defn.ModuleSerializationProxyConstructor,
                    List(Literal(Constant(clazz.sourceModule.termRef)))))
           .withSpan(ctx.owner.span.focus))
-    }
     else
       Nil
-  }
+
+  extension (cls: ClassSymbol) private def isEnumValueImplementation(using Context): Boolean =
+    derivesFrom(defn.EnumValueClass) && classParents.exists(_.typeSymbol.flags.is(Enum))
+
+  /** If this is the class backing a serializable singleton enum value with base class `MyEnum`,
+   *  and not deriving from `java.lang.Enum` add the method:
+   *
+   *      private def writeReplace(): AnyRef =
+   *        new scala.runtime.EnumValueSerializationProxy(classOf[MyEnum], this.ordinal)
+   *
+   *  unless an implementation already exists, otherwise do nothing.
+   */
+   def serializableEnumValueMethod(clazz: ClassSymbol)(using Context): List[Tree] =
+    if clazz.isEnumValueImplementation
+      && !clazz.derivesFrom(defn.JavaEnumClass)
+      && clazz.isSerializable
+      && !hasWriteReplace(clazz)
+    then
+      List(
+        DefDef(writeReplaceDef(clazz),
+          _ => New(defn.EnumValueSerializationProxyClass.typeRef,
+                   defn.EnumValueSerializationProxyConstructor,
+                   List(Literal(Constant(clazz.classParents.head)), This(clazz).select(nme.ordinal).ensureApplied)))
+          .withSpan(ctx.owner.span.focus))
+    else
+      Nil
 
   /** The class
    *
@@ -528,6 +555,6 @@ class SyntheticMembers(thisPhase: DenotTransformer) {
   def addSyntheticMembers(impl: Template)(using Context): Template = {
     val clazz = ctx.owner.asClass
     addMirrorSupport(
-      cpy.Template(impl)(body = serializableObjectMethod(clazz) ::: caseAndValueMethods(clazz) ::: impl.body))
+      cpy.Template(impl)(body = serializableObjectMethod(clazz) ::: serializableEnumValueMethod(clazz) ::: caseAndValueMethods(clazz) ::: impl.body))
   }
 }

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -1720,7 +1720,7 @@ class Typer extends Namer
             }
           if (desugaredArg.isType)
             arg match {
-              case TypeBoundsTree(EmptyTree, EmptyTree, _)
+              case untpd.WildcardTypeBoundsTree()
               if tparam.paramInfo.isLambdaSub &&
                  tpt1.tpe.typeParamSymbols.nonEmpty &&
                  !ctx.mode.is(Mode.Pattern) =>
@@ -1739,7 +1739,7 @@ class Typer extends Namer
         args.zipWithConserve(tparams)(typedArg(_, _)).asInstanceOf[List[Tree]]
       }
       val paramBounds = tparams.lazyZip(args).map {
-        case (tparam, TypeBoundsTree(EmptyTree, EmptyTree, _)) =>
+        case (tparam, untpd.WildcardTypeBoundsTree()) =>
           // if type argument is a wildcard, suppress kind checking since
           // there is no real argument.
           NoType

tests/neg/i6601.scala

@@ -7,4 +7,4 @@ object GADTs2 {
     case Lit[G](n: Int) extends Expr[G, Int]
         // case S[A, G](x:
   }
-}
+}