Java-compatible enums

compiler/src/dotty/tools/backend/jvm/BTypesFromSymbols.scala

@@ -223,7 +223,8 @@ class BTypesFromSymbols[I <: BackendInterface](val int: I) extends BTypes {
       if (sym.hasEnumFlag) ACC_ENUM else 0,
       if (sym.isVarargsMethod) ACC_VARARGS else 0,
       if (sym.isSynchronized) ACC_SYNCHRONIZED else 0,
-      if (sym.isDeprecated) asm.Opcodes.ACC_DEPRECATED else 0
+      if (sym.isDeprecated) asm.Opcodes.ACC_DEPRECATED else 0,
+      if (sym.isJavaEnum) asm.Opcodes.ACC_ENUM else 0
     )
   }
 

compiler/src/dotty/tools/backend/jvm/BackendInterface.scala

@@ -512,6 +512,7 @@ abstract class BackendInterface extends BackendInterfaceDefinitions {
     def isJavaDefaultMethod: Boolean
     def isClassConstructor: Boolean
     def isSerializable: Boolean
+    def isJavaEnum: Boolean
 
     /**
      * True for module classes of modules that are top-level or owned only by objects. Module classes

compiler/src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -703,6 +703,7 @@ class DottyBackendInterface(outputDirectory: AbstractFile, val superCallsMap: Ma
     def shouldEmitForwarders: Boolean =
       (sym is Flags.Module) && sym.isStatic
     def isJavaEntryPoint: Boolean = CollectEntryPoints.isJavaEntryPoint(sym)
+    def isJavaEnum = sym.derivesFromJavaEnum
 
     def isClassConstructor: Boolean = toDenot(sym).isClassConstructor
     def isSerializable: Boolean = toDenot(sym).isSerializable

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

@@ -545,7 +545,7 @@ object desugar {
         yield syntheticProperty(nme.selectorName(i), caseParams(i).tpt,
           Select(This(EmptyTypeIdent), caseParams(i).name))
       }
-      def enumTagMeths = if (isEnumCase) enumTagMeth(CaseKind.Class)._1 :: Nil else Nil
+      def ordinalMeths = if (isEnumCase) ordinalMethLit(nextOrdinal(CaseKind.Class)._1) :: Nil else Nil
       def copyMeths = {
         val hasRepeatedParam = constrVparamss.exists(_.exists {
           case ValDef(_, tpt, _) => isRepeated(tpt)
@@ -582,7 +582,7 @@ object desugar {
       }
 
       if (isCaseClass)
-        productElemNameMeth :: copyMeths ::: enumTagMeths ::: productElemMeths
+        productElemNameMeth :: copyMeths ::: ordinalMeths ::: productElemMeths
       else Nil
     }
 

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

@@ -74,57 +74,72 @@ object DesugarEnums {
     else if (isEnumCase(cdef)) cdef.withMods(cdef.mods.withFlags(cdef.mods.flags | Final))
     else cdef
 
-  private def valuesDot(name: String)(implicit src: SourceFile) =
+  private def valuesDot(name: PreName)(implicit src: SourceFile) =
     Select(Ident(nme.DOLLAR_VALUES), name.toTermName)
+
   private def registerCall(implicit ctx: Context): List[Tree] =
     if (enumClass.typeParams.nonEmpty) Nil
     else Apply(valuesDot("register"), This(EmptyTypeIdent) :: Nil) :: Nil
 
   /**  The following lists of definitions for an enum type E:
    *
    *   private val $values = new EnumValues[E]
-   *   def enumValue = $values.fromInt
-   *   def enumValueNamed = $values.fromName
-   *   def enumValues = $values.values
+   *   def valueOf($name: String) =
+   *     try $values.fromName($name) catch
+   *       {
+   *         case ex$:NoSuchElementException =>
+   *           throw new IllegalArgumentException("key not found: ".concat(name))
+   *       }
+   *   def values = $values.values.toArray
    */
   private def enumScaffolding(implicit ctx: Context): List[Tree] = {
-    def enumDefDef(name: String, select: String) =
-      DefDef(name.toTermName, Nil, Nil, TypeTree(), valuesDot(select))
+    val valuesDef =
+      DefDef(nme.values, Nil, Nil, TypeTree(), Select(valuesDot(nme.values), nme.toArray))
     val privateValuesDef =
       ValDef(nme.DOLLAR_VALUES, TypeTree(),
         New(TypeTree(defn.EnumValuesType.appliedTo(enumClass.typeRef :: Nil)), ListOfNil))
         .withFlags(Private)
-    val valueOfDef = enumDefDef("enumValue", "fromInt")
-    val withNameDef = enumDefDef("enumValueNamed", "fromName")
-    val valuesDef = enumDefDef("enumValues", "values")
-    List(privateValuesDef, valueOfDef, withNameDef, valuesDef)
+
+    val valuesOfExnMessage = Apply(
+      Select(Literal(Constant("key not found: ")), "concat".toTermName),
+      Ident(nme.nameDollar) :: Nil)
+    val valuesOfBody = Try(
+      expr = Apply(valuesDot("fromName"), Ident(nme.nameDollar) :: Nil),
+      cases = CaseDef(
+        pat = Typed(Ident(nme.DEFAULT_EXCEPTION_NAME), TypeTree(defn.NoSuchElementExceptionType)),
+        guard = EmptyTree,
+        body = Throw(New(TypeTree(defn.IllegalArgumentExceptionType), List(valuesOfExnMessage :: Nil)))
+      ) :: Nil,
+      finalizer = EmptyTree
+    )
+    val valueOfDef = DefDef(nme.valueOf, Nil, List(param(nme.nameDollar, defn.StringType) :: Nil),
+      TypeTree(), valuesOfBody)
+
+    valuesDef ::
+    privateValuesDef ::
+    valueOfDef :: Nil
   }
 
   /** A creation method for a value of enum type `E`, which is defined as follows:
    *
-   *   private def $new(tag: Int, name: String) = new E {
-   *     def enumTag = tag
-   *     override def toString = name
+   *   private def $new(_$ordinal: Int, $name: String) = new E {
+   *     def $ordinal = $tag
+   *     override def toString = $name
    *     $values.register(this)
    *   }
    */
   private def enumValueCreator(implicit ctx: Context) = {
-    def param(name: TermName, typ: Type) =
-      ValDef(name, TypeTree(typ), EmptyTree).withFlags(Param)
-    val enumTagDef =
-      DefDef(nme.enumTag, Nil, Nil, TypeTree(), Ident(nme.tag))
-    val toStringDef =
-      DefDef(nme.toString_, Nil, Nil, TypeTree(), Ident(nme.name))
-        .withFlags(Override)
+    val ordinalDef = ordinalMeth(Ident(nme.ordinalDollar_))
+    val toStringDef = toStringMeth(Ident(nme.nameDollar))
     val creator = New(Template(
       constr = emptyConstructor,
       parents = enumClassRef :: Nil,
       derived = Nil,
       self = EmptyValDef,
-      body = List(enumTagDef, toStringDef) ++ registerCall
+      body = List(ordinalDef, toStringDef) ++ registerCall
     ).withAttachment(ExtendsSingletonMirror, ()))
     DefDef(nme.DOLLAR_NEW, Nil,
-        List(List(param(nme.tag, defn.IntType), param(nme.name, defn.StringType))),
+        List(List(param(nme.ordinalDollar_, defn.IntType), param(nme.nameDollar, defn.StringType))),
         TypeTree(), creator).withFlags(Private | Synthetic)
   }
 
@@ -232,7 +247,7 @@ object DesugarEnums {
    *   - scaffolding containing the necessary definitions for singleton enum cases
    *     unless that scaffolding was already generated by a previous call to `nextEnumKind`.
    */
-  def nextEnumTag(kind: CaseKind.Value)(implicit ctx: Context): (Int, List[Tree]) = {
+  def nextOrdinal(kind: CaseKind.Value)(implicit ctx: Context): (Int, List[Tree]) = {
     val (count, seenKind) = ctx.tree.removeAttachment(EnumCaseCount).getOrElse((0, CaseKind.Class))
     val minKind = if (kind < seenKind) kind else seenKind
     ctx.tree.pushAttachment(EnumCaseCount, (count + 1, minKind))
@@ -244,14 +259,20 @@ object DesugarEnums {
     (count, scaffolding)
   }
 
-  /** A pair consisting of
-   *   - a method returning the next enum tag
-   *   - scaffolding as defined in `nextEnumTag`
-   */
-  def enumTagMeth(kind: CaseKind.Value)(implicit ctx: Context): (DefDef, List[Tree]) = {
-    val (tag, scaffolding) = nextEnumTag(kind)
-    (DefDef(nme.enumTag, Nil, Nil, TypeTree(), Literal(Constant(tag))), scaffolding)
-  }
+  def param(name: TermName, typ: Type)(implicit ctx: Context) =
+    ValDef(name, TypeTree(typ), EmptyTree).withFlags(Param)
+
+  def ordinalMeth(body: Tree)(implicit ctx: Context): DefDef =
+    DefDef(nme.ordinalDollar, Nil, Nil, TypeTree(defn.IntType), body)
+
+  def toStringMeth(body: Tree)(implicit ctx: Context): DefDef =
+    DefDef(nme.toString_, Nil, Nil, TypeTree(defn.StringType), body).withFlags(Override)
+
+  def ordinalMethLit(ord: Int)(implicit ctx: Context): DefDef =
+    ordinalMeth(Literal(Constant(ord)))
+
+  def toStringMethLit(name: String)(implicit ctx: Context): DefDef =
+    toStringMeth(Literal(Constant(name)))
 
   /** Expand a module definition representing a parameterless enum case */
   def expandEnumModule(name: TermName, impl: Template, mods: Modifiers, span: Span)(implicit ctx: Context): Tree = {
@@ -260,11 +281,10 @@ object DesugarEnums {
     else if (impl.parents.isEmpty)
       expandSimpleEnumCase(name, mods, span)
     else {
-      def toStringMeth =
-        DefDef(nme.toString_, Nil, Nil, TypeTree(defn.StringType), Literal(Constant(name.toString)))
-          .withFlags(Override)
-      val (tagMeth, scaffolding) = enumTagMeth(CaseKind.Object)
-      val impl1 = cpy.Template(impl)(body = List(tagMeth, toStringMeth) ++ registerCall)
+      val (tag, scaffolding) = nextOrdinal(CaseKind.Object)
+      val ordinalDef = ordinalMethLit(tag)
+      val toStringDef = toStringMethLit(name.toString)
+      val impl1 = cpy.Template(impl)(body = List(ordinalDef, toStringDef) ++ registerCall)
         .withAttachment(ExtendsSingletonMirror, ())
       val vdef = ValDef(name, TypeTree(), New(impl1)).withMods(mods | Final)
       flatTree(scaffolding ::: vdef :: Nil).withSpan(span)
@@ -280,7 +300,7 @@ object DesugarEnums {
       expandEnumModule(name, impl, mods, span)
     }
     else {
-      val (tag, scaffolding) = nextEnumTag(CaseKind.Simple)
+      val (tag, scaffolding) = nextOrdinal(CaseKind.Simple)
       val creator = Apply(Ident(nme.DOLLAR_NEW), List(Literal(Constant(tag)), Literal(Constant(name.toString))))
       val vdef = ValDef(name, enumClassRef, creator).withMods(mods | Final)
       flatTree(scaffolding ::: vdef :: Nil).withSpan(span)

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

@@ -605,6 +605,11 @@ class Definitions {
   @threadUnsafe lazy val SystemClass: ClassSymbol               = ctx.requiredClass("java.lang.System")
   @threadUnsafe lazy val SystemModule: Symbol              = SystemClass.linkedClass
 
+  @threadUnsafe lazy val NoSuchElementExceptionClass = ctx.requiredClass("java.util.NoSuchElementException")
+  def NoSuchElementExceptionType = NoSuchElementExceptionClass.typeRef
+  @threadUnsafe lazy val IllegalArgumentExceptionClass = ctx.requiredClass("java.lang.IllegalArgumentException")
+  def IllegalArgumentExceptionType = IllegalArgumentExceptionClass.typeRef
+
   // in scalac modified to have Any as parent
 
   @threadUnsafe lazy val ThrowableType: TypeRef          = ctx.requiredClassRef("java.lang.Throwable")
@@ -701,6 +706,8 @@ class Definitions {
   def NoneClass(implicit ctx: Context): ClassSymbol = NoneModuleRef.symbol.moduleClass.asClass
   @threadUnsafe lazy val EnumType: TypeRef                    = ctx.requiredClassRef("scala.Enum")
   def EnumClass(implicit ctx: Context): ClassSymbol = EnumType.symbol.asClass
+    @threadUnsafe lazy val Enum_ordinalR: TermRef = EnumClass.requiredMethodRef(nme.ordinal)
+    def Enum_ordinal(implicit ctx: Context): Symbol = Enum_ordinalR.symbol
   @threadUnsafe lazy val EnumValuesType: TypeRef              = ctx.requiredClassRef("scala.runtime.EnumValues")
   def EnumValuesClass(implicit ctx: Context): ClassSymbol = EnumValuesType.symbol.asClass
   @threadUnsafe lazy val ProductType: TypeRef                 = ctx.requiredClassRef("scala.Product")

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

@@ -420,7 +420,6 @@ object StdNames {
     val elems: N                = "elems"
     val emptyValDef: N          = "emptyValDef"
     val ensureAccessible : N    = "ensureAccessible"
-    val enumTag: N              = "enumTag"
     val eq: N                   = "eq"
     val eqInstance: N           = "eqInstance"
     val equalsNumChar : N       = "equalsNumChar"
@@ -485,6 +484,7 @@ object StdNames {
     val mirror : N              = "mirror"
     val moduleClass : N         = "moduleClass"
     val name: N                 = "name"
+    val nameDollar: N           = "$name"
     val ne: N                   = "ne"
     val newFreeTerm: N          = "newFreeTerm"
     val newFreeType: N          = "newFreeType"
@@ -500,6 +500,8 @@ object StdNames {
     val ofDim: N                = "ofDim"
     val opaque: N               = "opaque"
     val ordinal: N              = "ordinal"
+    val ordinalDollar: N        = "$ordinal"
+    val ordinalDollar_ : N      = "_$ordinal"
     val origin: N               = "origin"
     val prefix : N              = "prefix"
     val productArity: N         = "productArity"

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

@@ -13,12 +13,13 @@ import Constants._
 import Decorators._
 import DenotTransformers._
 import dotty.tools.dotc.ast.Trees._
+import SymUtils._
 
 object CompleteJavaEnums {
   val name: String = "completeJavaEnums"
 
-  private val nameParamName: TermName = "$name".toTermName
-  private val ordinalParamName: TermName = "$ordinal".toTermName
+  private val nameParamName: TermName = "_$name".toTermName
+  private val ordinalParamName: TermName = "_$ordinal".toTermName
 }
 
 /** For Scala enums that inherit from java.lang.Enum:
@@ -37,16 +38,10 @@ class CompleteJavaEnums extends MiniPhase with InfoTransformer { thisPhase =>
   def transformInfo(tp: Type, sym: Symbol)(implicit ctx: Context): Type =
     if (sym.isConstructor && (
          sym == defn.JavaEnumClass.primaryConstructor ||
-         derivesFromJavaEnum(sym.owner)))
+         sym.owner.derivesFromJavaEnum))
       addConstrParams(sym.info)
     else tp
 
-  /** Is `sym` a Scala enum class that derives (directly) from `java.lang.Enum`?
-   */
-  private def derivesFromJavaEnum(sym: Symbol)(implicit ctx: Context) =
-    sym.is(Enum, butNot = Case) &&
-    sym.info.parents.exists(p => p.typeSymbol == defn.JavaEnumClass)
-
   /** Add constructor parameters `$name: String` and `$ordinal: Int` to the end of
    *  the last parameter list of (method- or poly-) type `tp`.
    */
@@ -87,24 +82,24 @@ class CompleteJavaEnums extends MiniPhase with InfoTransformer { thisPhase =>
    *  2. If this is a $new method that creates simple cases, pass $name and $ordinal parameters
    *     to the enum superclass. The $new method looks like this:
    *
-   *       def $new(..., enumTag: Int, name: String) = {
+   *       def $new(..., ordinal: Int, name: String) = {
    *         class $anon extends E(...) { ... }
    *         new $anon
    *       }
    *
    *     After the transform it is expanded to
    *
-   *       def $new(..., enumTag: Int, name: String) = {
-   *         class $anon extends E(..., name, enumTag) { ... }
+   *       def $new(..., ordinal: Int, name: String) = {
+   *         class $anon extends E(..., name, ordinal) { ... }
    *         new $anon
    *       }
    */
   override def transformDefDef(tree: DefDef)(implicit ctx: Context): DefDef = {
     val sym = tree.symbol
-    if (sym.isConstructor && derivesFromJavaEnum(sym.owner))
+    if (sym.isConstructor && sym.owner.derivesFromJavaEnum)
       cpy.DefDef(tree)(
         vparamss = tree.vparamss.init :+ (tree.vparamss.last ++ addedParams(sym, Param)))
-    else if (sym.name == nme.DOLLAR_NEW && derivesFromJavaEnum(sym.owner.linkedClass)) {
+    else if (sym.name == nme.DOLLAR_NEW && sym.owner.linkedClass.derivesFromJavaEnum) {
       val Block((tdef @ TypeDef(tpnme.ANON_CLASS, templ: Template)) :: Nil, call) = tree.rhs
       val args = tree.vparamss.last.takeRight(2).map(param => ref(param.symbol)).reverse
       val templ1 = cpy.Template(templ)(
@@ -124,7 +119,7 @@ class CompleteJavaEnums extends MiniPhase with InfoTransformer { thisPhase =>
    *
    *       class $anon extends E(...) {
    *          ...
-   *          def enumTag = N
+   *          def ordinal = N
    *          def toString = S
    *          ...
    *       }
@@ -137,20 +132,20 @@ class CompleteJavaEnums extends MiniPhase with InfoTransformer { thisPhase =>
    */
   override def transformTemplate(templ: Template)(implicit ctx: Context): Template = {
     val cls = templ.symbol.owner
-    if (derivesFromJavaEnum(cls)) {
+    if (cls.derivesFromJavaEnum) {
       val (params, rest) = decomposeTemplateBody(templ.body)
       val addedDefs = addedParams(cls, ParamAccessor)
       val addedSyms = addedDefs.map(_.symbol.entered)
       cpy.Template(templ)(
         parents = addEnumConstrArgs(defn.JavaEnumClass, templ.parents, addedSyms.map(ref)),
         body = params ++ addedDefs ++ rest)
     }
-    else if (cls.isAnonymousClass && cls.owner.is(EnumCase) && derivesFromJavaEnum(cls.owner.owner.linkedClass)) {
+    else if (cls.isAnonymousClass && cls.owner.is(EnumCase) && cls.owner.owner.linkedClass.derivesFromJavaEnum) {
       def rhsOf(name: TermName) =
         templ.body.collect {
           case mdef: DefDef if mdef.name == name => mdef.rhs
         }.head
-      val args = List(rhsOf(nme.toString_), rhsOf(nme.enumTag))
+      val args = List(rhsOf(nme.toString_), rhsOf(nme.ordinalDollar))
       cpy.Template(templ)(
         parents = addEnumConstrArgs(cls.owner.owner.linkedClass, templ.parents, args))
     }

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

@@ -67,6 +67,10 @@ class SymUtils(val self: Symbol) extends AnyVal {
   def isParamOrAccessor(implicit ctx: Context): Boolean =
     self.is(Param) || self.is(ParamAccessor)
 
+  def derivesFromJavaEnum(implicit ctx: Context) =
+    self.is(Enum, butNot = Case) &&
+    self.info.parents.exists(p => p.typeSymbol == defn.JavaEnumClass)
+
   /** Is this a case class for which a product mirror is generated?
    *  Excluded are value classes, abstract classes and case classes with more than one
    *  parameter section.