Use some enums in compiler

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

@@ -26,26 +26,22 @@ object desugar {
   /** If a Select node carries this attachment, suppress the check
    *  that its type refers to an acessible symbol.
    */
-  val SuppressAccessCheck: Property.Key[Unit] = new Property.Key
+  val SuppressAccessCheck: Property.Key[Unit] = Property.Key()
 
   /** An attachment for companion modules of classes that have a `derives` clause.
    *  The position value indicates the start position of the template of the
    *  deriving class.
    */
-  val DerivingCompanion: Property.Key[SourcePosition] = new Property.Key
+  val DerivingCompanion: Property.Key[SourcePosition] = Property.Key()
 
   /** An attachment for match expressions generated from a PatDef or GenFrom.
    *  Value of key == one of IrrefutablePatDef, IrrefutableGenFrom
    */
-  val CheckIrrefutable: Property.Key[MatchCheck] = new Property.StickyKey
-
-  /** What static check should be applied to a Match (none, irrefutable, exhaustive) */
-  class MatchCheck(val n: Int) extends AnyVal
-  object MatchCheck {
-    val None = new MatchCheck(0)
-    val Exhaustive = new MatchCheck(1)
-    val IrrefutablePatDef = new MatchCheck(2)
-    val IrrefutableGenFrom = new MatchCheck(3)
+  val CheckIrrefutable: Property.Key[MatchCheck] = Property.StickyKey()
+
+  /** What static check should be applied to a Match? */
+  enum MatchCheck {
+    case None, Exhaustive, IrrefutablePatDef, IrrefutableGenFrom
   }
 
   /** Info of a variable in a pattern: The named tree and its type */
@@ -136,17 +132,17 @@ object desugar {
   def derivedTypeParam(tdef: TypeDef, suffix: String = "")(implicit ctx: Context): TypeDef =
     cpy.TypeDef(tdef)(
       name = tdef.name ++ suffix,
-      rhs = new DerivedFromParamTree(suffix).withSpan(tdef.rhs.span).watching(tdef)
+      rhs = DerivedFromParamTree(suffix).withSpan(tdef.rhs.span).watching(tdef)
     )
 
   /** A derived type definition watching `sym` */
   def derivedTypeParam(sym: TypeSymbol)(implicit ctx: Context): TypeDef =
-    TypeDef(sym.name, new DerivedFromParamTree("").watching(sym)).withFlags(TypeParam)
+    TypeDef(sym.name, DerivedFromParamTree("").watching(sym)).withFlags(TypeParam)
 
   /** A value definition copied from `vdef` with a tpt typetree derived from it */
   def derivedTermParam(vdef: ValDef)(implicit ctx: Context): ValDef =
     cpy.ValDef(vdef)(
-      tpt = new DerivedFromParamTree("").withSpan(vdef.tpt.span).watching(vdef))
+      tpt = DerivedFromParamTree("").withSpan(vdef.tpt.span).watching(vdef))
 
 // ----- Desugar methods -------------------------------------------------
 
@@ -165,7 +161,7 @@ object desugar {
       // val getter = ValDef(mods, name, tpt, rhs) withPos vdef.pos?
       // right now vdef maps via expandedTree to a thicket which concerns itself.
       // I don't see a problem with that but if there is one we can avoid it by making a copy here.
-      val setterParam = makeSyntheticParameter(tpt = (new SetterParamTree).watching(vdef))
+      val setterParam = makeSyntheticParameter(tpt = SetterParamTree().watching(vdef))
       // The rhs gets filled in later, when field is generated and getter has parameters (see Memoize miniphase)
       val setterRhs = if (vdef.rhs.isEmpty) EmptyTree else unitLiteral
       val setter = cpy.DefDef(vdef)(
@@ -217,7 +213,7 @@ object desugar {
     val meth @ DefDef(_, tparams, vparamss, tpt, rhs) = transformQuotedPatternName(meth0)
     val methName = normalizeName(meth, tpt).asTermName
     val mods = meth.mods
-    val epbuf = new ListBuffer[ValDef]
+    val epbuf = ListBuffer[ValDef]()
     def desugarContextBounds(rhs: Tree): Tree = rhs match {
       case ContextBounds(tbounds, cxbounds) =>
         epbuf ++= makeImplicitParameters(cxbounds, Implicit, forPrimaryConstructor = isPrimaryConstructor)
@@ -443,7 +439,7 @@ object desugar {
         val (enumCases, enumStats) = stats.partition(DesugarEnums.isEnumCase)
         if (enumCases.isEmpty)
           ctx.error("Enumerations must constain at least one case", namePos)
-        val enumCompanionRef = new TermRefTree()
+        val enumCompanionRef = TermRefTree()
         val enumImport = Import(importDelegate = false, enumCompanionRef, enumCases.flatMap(caseIds))
         (enumImport :: enumStats, enumCases, enumCompanionRef)
       }
@@ -456,7 +452,7 @@ object desugar {
     val derivedVparamss = constrVparamss.nestedMap(derivedTermParam(_))
     val arity = constrVparamss.head.length
 
-    val classTycon: Tree = new TypeRefTree // watching is set at end of method
+    val classTycon: Tree = TypeRefTree() // watching is set at end of method
 
     def appliedTypeTree(tycon: Tree, args: List[Tree]) =
       (if (args.isEmpty) tycon else AppliedTypeTree(tycon, args))
@@ -895,8 +891,8 @@ object desugar {
         }
       else x
   }
-  private val typeNameExtractor = new NameExtractor(followArgs = true)
-  private val argNameExtractor = new NameExtractor(followArgs = false)
+  private val typeNameExtractor = NameExtractor(followArgs = true)
+  private val argNameExtractor = NameExtractor(followArgs = false)
 
   private def inventTypeName(tree: Tree)(implicit ctx: Context): String = typeNameExtractor("", tree)
 
@@ -1207,7 +1203,7 @@ object desugar {
   def makeContextualFunction(formals: List[Type], body: Tree, isErased: Boolean)(implicit ctx: Context): Tree = {
     val mods = if (isErased) Given | Erased else Given
     val params = makeImplicitParameters(formals.map(TypeTree), mods)
-    new FunctionWithMods(params, body, Modifiers(mods))
+    FunctionWithMods(params, body, Modifiers(mods))
   }
 
   /** Add annotation to tree:
@@ -1419,7 +1415,7 @@ object desugar {
           val pdefs = (valeqs, defpats, rhss).zipped.map(makePatDef(_, Modifiers(), _, _))
           val rhs1 = makeFor(nme.map, nme.flatMap, GenFrom(defpat0, gen.expr, gen.checkMode) :: Nil, Block(pdefs, makeTuple(id0 :: ids)))
           val allpats = gen.pat :: pats
-          val vfrom1 = new GenFrom(makeTuple(allpats), rhs1, GenCheckMode.Ignore)
+          val vfrom1 = GenFrom(makeTuple(allpats), rhs1, GenCheckMode.Ignore)
           makeFor(mapName, flatMapName, vfrom1 :: rest1, body)
         case (gen: GenFrom) :: test :: rest =>
           val filtered = Apply(rhsSelect(gen, nme.withFilter), makeLambda(gen, test))
@@ -1594,7 +1590,7 @@ object desugar {
    *  without duplicates
    */
   private def getVariables(tree: Tree)(implicit ctx: Context): List[VarInfo] = {
-    val buf = new ListBuffer[VarInfo]
+    val buf = ListBuffer[VarInfo]()
     def seenName(name: Name) = buf exists (_._1.name == name)
     def add(named: NameTree, t: Tree): Unit =
       if (!seenName(named.name) && named.name.isTermName) buf += ((named, t))

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

@@ -21,7 +21,7 @@ object DesugarEnums {
   }
 
   /** Attachment containing the number of enum cases and the smallest kind that was seen so far. */
-  val EnumCaseCount: Property.Key[(Int, DesugarEnums.CaseKind.Value)] = new Property.Key
+  val EnumCaseCount: Property.Key[(Int, DesugarEnums.CaseKind.Value)] = Property.Key()
 
   /** The enumeration class that belongs to an enum case. This works no matter
    *  whether the case is still in the enum class or it has been transferred to the

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

@@ -83,7 +83,7 @@ object Trees {
      */
     final def tpe: T @uncheckedVariance = {
       if (myTpe == null)
-        throw new UnAssignedTypeException(this)
+        throw UnAssignedTypeException(this)
       myTpe
     }
 
@@ -857,19 +857,19 @@ object Trees {
 
   class EmptyTree[T >: Untyped] extends Thicket(Nil)(NoSource) {
     // assert(uniqueId != 1492)
-    override def withSpan(span: Span) = throw new AssertionError("Cannot change span of EmptyTree")
+    override def withSpan(span: Span) = throw AssertionError("Cannot change span of EmptyTree")
   }
 
   class EmptyValDef[T >: Untyped] extends ValDef[T](
     nme.WILDCARD, genericEmptyTree[T], genericEmptyTree[T])(NoSource) with WithoutTypeOrPos[T] {
     myTpe = NoType.asInstanceOf[T]
     setMods(untpd.Modifiers(PrivateLocal))
     override def isEmpty: Boolean = true
-    override def withSpan(span: Span) = throw new AssertionError("Cannot change span of EmptyValDef")
+    override def withSpan(span: Span) = throw AssertionError("Cannot change span of EmptyValDef")
   }
 
-  @sharable val theEmptyTree: EmptyTree[Type] = new EmptyTree[Type]
-  @sharable val theEmptyValDef: EmptyValDef[Type] = new EmptyValDef[Type]
+  @sharable val theEmptyTree = new EmptyTree[Type]()
+  @sharable val theEmptyValDef = new EmptyValDef[Type]()
 
   def genericEmptyValDef[T >: Untyped]: ValDef[T]       = theEmptyValDef.asInstanceOf[ValDef[T]]
   def genericEmptyTree[T >: Untyped]: Thicket[T]        = theEmptyTree.asInstanceOf[Thicket[T]]
@@ -992,11 +992,10 @@ object Trees {
 
     @sharable val EmptyTree: Thicket = genericEmptyTree
     @sharable val EmptyValDef: ValDef = genericEmptyValDef
-    @sharable val ContextualEmptyTree: Thicket = new EmptyTree // an empty tree marking a contextual closure
+    @sharable val ContextualEmptyTree: Thicket = EmptyTree() // an empty tree marking a contextual closure
 
     // ----- Auxiliary creation methods ------------------
 
-    def Thicket(trees: List[Tree])(implicit src: SourceFile): Thicket = new Thicket(trees)
     def Thicket(): Thicket = EmptyTree
     def Thicket(x1: Tree, x2: Tree)(implicit src: SourceFile): Thicket = Thicket(x1 :: x2 :: Nil)
     def Thicket(x1: Tree, x2: Tree, x3: Tree)(implicit src: SourceFile): Thicket = Thicket(x1 :: x2 :: x3 :: Nil)
@@ -1036,7 +1035,7 @@ object Trees {
       def Select(tree: Tree)(qualifier: Tree, name: Name)(implicit ctx: Context): Select = tree match {
         case tree: SelectWithSig =>
           if ((qualifier eq tree.qualifier) && (name == tree.name)) tree
-          else finalize(tree, new SelectWithSig(qualifier, name, tree.sig)(sourceFile(tree)))
+          else finalize(tree, SelectWithSig(qualifier, name, tree.sig)(sourceFile(tree)))
         case tree: Select if (qualifier eq tree.qualifier) && (name == tree.name) => tree
         case _ => finalize(tree, untpd.Select(qualifier, name)(sourceFile(tree)))
       }

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

@@ -153,7 +153,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     ta.assignType(untpd.SeqLiteral(elems, elemtpt), elems, elemtpt)
 
   def JavaSeqLiteral(elems: List[Tree], elemtpt: Tree)(implicit ctx: Context): JavaSeqLiteral =
-    ta.assignType(new untpd.JavaSeqLiteral(elems, elemtpt), elems, elemtpt).asInstanceOf[JavaSeqLiteral]
+    ta.assignType(untpd.JavaSeqLiteral(elems, elemtpt), elems, elemtpt).asInstanceOf[JavaSeqLiteral]
 
   def Inlined(call: Tree, bindings: List[MemberDef], expansion: Tree)(implicit ctx: Context): Inlined =
     ta.assignType(untpd.Inlined(call, bindings, expansion), bindings, expansion)
@@ -231,7 +231,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     def valueParamss(tp: Type): (List[List[TermSymbol]], Type) = tp match {
       case tp: MethodType =>
         val isParamDependent = tp.isParamDependent
-        val previousParamRefs = if (isParamDependent) new mutable.ListBuffer[TermRef]() else null
+        val previousParamRefs = if (isParamDependent) mutable.ListBuffer[TermRef]() else null
 
         def valueParam(name: TermName, origInfo: Type): TermSymbol = {
           val maybeImplicit =
@@ -294,7 +294,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     val newTypeParams =
       for (tparam <- cls.typeParams if !(bodyTypeParams contains tparam))
       yield TypeDef(tparam)
-    val findLocalDummy = new FindLocalDummyAccumulator(cls)
+    val findLocalDummy = FindLocalDummyAccumulator(cls)
     val localDummy = ((NoSymbol: Symbol) /: body)(findLocalDummy.apply)
       .orElse(ctx.newLocalDummy(cls))
     val impl = untpd.Template(constr, parents, Nil, selfType, newTypeParams ++ body)
@@ -391,7 +391,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   private def followOuterLinks(t: Tree)(implicit ctx: Context) = t match {
     case t: This if ctx.erasedTypes && !(t.symbol == ctx.owner.enclosingClass || t.symbol.isStaticOwner) =>
       // after erasure outer paths should be respected
-      new ExplicitOuter.OuterOps(ctx).path(toCls = t.tpe.widen.classSymbol)
+      ExplicitOuter.OuterOps(ctx).path(toCls = t.tpe.widen.classSymbol)
     case t =>
       t
   }
@@ -538,9 +538,9 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   }
 
   override val cpy: TypedTreeCopier = // Type ascription needed to pick up any new members in TreeCopier (currently there are none)
-    new TypedTreeCopier
+    TypedTreeCopier()
 
-  val cpyBetweenPhases: TimeTravellingTreeCopier = new TimeTravellingTreeCopier
+  val cpyBetweenPhases: TimeTravellingTreeCopier = TimeTravellingTreeCopier()
 
   class TypedTreeCopier extends TreeCopier {
     def postProcess(tree: Tree, copied: untpd.Tree): copied.ThisTree[Type] =
@@ -746,16 +746,16 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     }
 
     def shallowFold[T](z: T)(op: (T, tpd.Tree) => T)(implicit ctx: Context): T =
-      new ShallowFolder(op).apply(z, tree)
+      ShallowFolder(op).apply(z, tree)
 
     def deepFold[T](z: T)(op: (T, tpd.Tree) => T)(implicit ctx: Context): T =
-      new DeepFolder(op).apply(z, tree)
+      DeepFolder(op).apply(z, tree)
 
     def find[T](pred: (tpd.Tree) => Boolean)(implicit ctx: Context): Option[tpd.Tree] =
       shallowFold[Option[tpd.Tree]](None)((accum, tree) => if (pred(tree)) Some(tree) else accum)
 
     def subst(from: List[Symbol], to: List[Symbol])(implicit ctx: Context): ThisTree =
-      new TreeTypeMap(substFrom = from, substTo = to).apply(tree)
+      TreeTypeMap(substFrom = from, substTo = to).apply(tree)
 
     /** Change owner from `from` to `to`. If `from` is a weak owner, also change its
      *  owner to `to`, and continue until a non-weak owner is reached.
@@ -766,7 +766,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
           loop(from.owner, from :: froms, to :: tos)
         else {
           //println(i"change owner ${from :: froms}%, % ==> $tos of $tree")
-          new TreeTypeMap(oldOwners = from :: froms, newOwners = tos).apply(tree)
+          TreeTypeMap(oldOwners = from :: froms, newOwners = tos).apply(tree)
         }
       }
       if (from == to) tree else loop(from, Nil, to :: Nil)
@@ -788,7 +788,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       }
       val owners = ownerAcc(immutable.Set.empty[Symbol], tree).toList
       val newOwners = List.fill(owners.size)(newOwner)
-      new TreeTypeMap(oldOwners = owners, newOwners = newOwners).apply(tree)
+      TreeTypeMap(oldOwners = owners, newOwners = newOwners).apply(tree)
     }
 
     /** After phase `trans`, set the owner of every definition in this tree that was formerly
@@ -1008,7 +1008,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     }
 
     /** Replace Ident nodes references to the underlying tree that defined them */
-    def underlying(implicit ctx: Context): Tree = new MapToUnderlying().transform(tree)
+    def underlying(implicit ctx: Context): Tree = MapToUnderlying().transform(tree)
 
     // --- Higher order traversal methods -------------------------------
 
@@ -1030,7 +1030,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
 
     /** All subtrees of this tree that satisfy predicate `p`. */
     def filterSubTrees(f: Tree => Boolean)(implicit ctx: Context): List[Tree] = {
-      val buf = new mutable.ListBuffer[Tree]
+      val buf = mutable.ListBuffer[Tree]()
       foreachSubTree { tree => if (f(tree)) buf += tree }
       buf.toList
     }
@@ -1137,7 +1137,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   def applyOverloaded(receiver: Tree, method: TermName, args: List[Tree], targs: List[Type],
                       expectedType: Type, isContextual: Boolean = false)(implicit ctx: Context): Tree = {
     val typer = ctx.typer
-    val proto = new FunProtoTyped(args, expectedType)(typer, isContextual)
+    val proto = FunProtoTyped(args, expectedType)(typer, isContextual)
     val denot = receiver.tpe.member(method)
     assert(denot.exists, i"no member $receiver . $method, members = ${receiver.tpe.decls}")
     val selected =
@@ -1162,7 +1162,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     val fun = receiver.select(selected).appliedToTypes(targs)
 
     val apply = untpd.Apply(fun, args)
-    new typer.ApplyToTyped(apply, fun, selected, args, expectedType).result.asInstanceOf[Tree] // needed to handle varargs
+    typer.ApplyToTyped(apply, fun, selected, args, expectedType).result.asInstanceOf[Tree] // needed to handle varargs
   }
 
   @tailrec
@@ -1221,7 +1221,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   }
 
   /** A key to be used in a context property that tracks enclosing inlined calls */
-  private val InlinedCalls = new Property.Key[List[Tree]]
+  private val InlinedCalls = Property.Key[List[Tree]]()
 
   /** Record an enclosing inlined call.
    *  EmptyTree calls (for parameters) cancel the next-enclosing call in the list instead of being added to it.

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

@@ -123,12 +123,11 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   class XMLBlock(stats: List[Tree], expr: Tree)(implicit @constructorOnly src: SourceFile) extends Block(stats, expr)
 
   /** An enum to control checking or filtering of patterns in GenFrom trees */
-  class GenCheckMode(val x: Int) extends AnyVal
-  object GenCheckMode {
-    val Ignore = new GenCheckMode(0)  // neither filter nor check since filtering was done before
-    val Check = new GenCheckMode(1)   // check that pattern is irrefutable
-    val FilterNow = new GenCheckMode(2)  // filter out non-matching elements since we are not in -strict
-    val FilterAlways = new GenCheckMode(3) // filter out non-matching elements since pattern is prefixed by `case`
+  enum GenCheckMode {
+    case Ignore       // neither filter nor check since filtering was done before
+    case Check        // check that pattern is irrefutable
+    case FilterNow    //filter out non-matching elements since we are not in -strict
+    case FilterAlways // filter out non-matching elements since pattern is prefixed by `case`
   }
 
   // ----- Modifiers -----------------------------------------------------
@@ -247,7 +246,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
     def isEnumClass: Boolean = isEnum && !is(Case)
   }
 
-  @sharable val EmptyModifiers: Modifiers = new Modifiers()
+  @sharable val EmptyModifiers: Modifiers = Modifiers()
 
   // ----- TypeTrees that refer to other tree's symbols -------------------
 
@@ -285,16 +284,16 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
    *  from the symbol in this type. These type trees have marker trees
    *  TypeRefOfSym or InfoOfSym as their originals.
    */
-  val References: Property.Key[List[DerivedTypeTree]] = new Property.Key
+  val References: Property.Key[List[DerivedTypeTree]] = Property.Key()
 
   /** Property key for TypeTrees marked with TypeRefOfSym or InfoOfSym
    *  which contains the symbol of the original tree from which this
    *  TypeTree is derived.
    */
-  val OriginalSymbol: Property.Key[Symbol] = new Property.Key
+  val OriginalSymbol: Property.Key[Symbol] = Property.Key()
 
   /** Property key for contextual Apply trees of the form `fn given arg` */
-  val ApplyGiven: Property.StickyKey[Unit] = new Property.StickyKey
+  val ApplyGiven: Property.StickyKey[Unit] = Property.StickyKey()
 
   // ------ Creation methods for untyped only -----------------
 
@@ -461,7 +460,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
 
 // --------- Copier/Transformer/Accumulator classes for untyped trees -----
 
-  override val cpy: UntypedTreeCopier = new UntypedTreeCopier
+  override val cpy: UntypedTreeCopier = UntypedTreeCopier()
 
   class UntypedTreeCopier extends TreeCopier {