[WIP] Direct representation of higher-kinded types

docs/SyntaxSummary.txt

@@ -96,6 +96,7 @@ grammar.
   ClassQualifier    ::=  `[' id `]'
 
   Type              ::=  FunArgTypes `=>' Type                                  Function(ts, t)
+                      |  HkTypeParamClause `->' Type						    TypeLambda(ps, t)
                       |  InfixType
   FunArgTypes       ::=  InfixType
                       | `(' [ FunArgType {`,' FunArgType } ] `)'
@@ -125,7 +126,6 @@ grammar.
   TypeParamBounds   ::=  TypeBounds {`<%' Type} {`:' Type}                      ContextBounds(typeBounds, tps)
 
   Expr              ::=  FunParams `=>' Expr                                    Function(args, expr), Function(ValDef([implicit], id, TypeTree(), EmptyTree), expr)
-                      |  Expr1
   FunParams         ::=  Bindings
                       |  [`implicit'] id
                       |  `_'

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

@@ -66,7 +66,7 @@ object desugar {
       val relocate = new TypeMap {
         val originalOwner = sym.owner
         def apply(tp: Type) = tp match {
-          case tp: NamedType if tp.symbol.owner eq originalOwner =>
+          case tp: NamedType if tp.symbol.exists && (tp.symbol.owner eq originalOwner) =>
             val defctx = ctx.outersIterator.dropWhile(_.scope eq ctx.scope).next
             var local = defctx.denotNamed(tp.name).suchThat(_ is ParamOrAccessor).symbol
             if (local.exists) (defctx.owner.thisType select local).dealias

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

@@ -594,6 +594,12 @@ object Trees {
     def forwardTo = tpt
   }
 
+  /** [typeparams] -> tpt */
+  case class TypeLambdaTree[-T >: Untyped] private[ast] (tparams: List[TypeDef[T]], body: Tree[T])
+    extends TypTree[T] {
+    type ThisTree[-T >: Untyped] = TypeLambdaTree[T]
+  }
+
   /** => T */
   case class ByNameTypeTree[-T >: Untyped] private[ast] (result: Tree[T])
   extends TypTree[T] {
@@ -851,6 +857,7 @@ object Trees {
     type OrTypeTree = Trees.OrTypeTree[T]
     type RefinedTypeTree = Trees.RefinedTypeTree[T]
     type AppliedTypeTree = Trees.AppliedTypeTree[T]
+    type TypeLambdaTree = Trees.TypeLambdaTree[T]
     type ByNameTypeTree = Trees.ByNameTypeTree[T]
     type TypeBoundsTree = Trees.TypeBoundsTree[T]
     type Bind = Trees.Bind[T]
@@ -1028,6 +1035,10 @@ object Trees {
         case tree: AppliedTypeTree if (tpt eq tree.tpt) && (args eq tree.args) => tree
         case _ => finalize(tree, untpd.AppliedTypeTree(tpt, args))
       }
+      def TypeLambdaTree(tree: Tree)(tparams: List[TypeDef], body: Tree): TypeLambdaTree = tree match {
+        case tree: TypeLambdaTree if (tparams eq tree.tparams) && (body eq tree.body) => tree
+        case _ => finalize(tree, untpd.TypeLambdaTree(tparams, body))
+      }
       def ByNameTypeTree(tree: Tree)(result: Tree): ByNameTypeTree = tree match {
         case tree: ByNameTypeTree if result eq tree.result => tree
         case _ => finalize(tree, untpd.ByNameTypeTree(result))
@@ -1160,6 +1171,8 @@ object Trees {
           cpy.RefinedTypeTree(tree)(transform(tpt), transformSub(refinements))
         case AppliedTypeTree(tpt, args) =>
           cpy.AppliedTypeTree(tree)(transform(tpt), transform(args))
+        case TypeLambdaTree(tparams, body) =>
+          cpy.TypeLambdaTree(tree)(transformSub(tparams), transform(body))
         case ByNameTypeTree(result) =>
           cpy.ByNameTypeTree(tree)(transform(result))
         case TypeBoundsTree(lo, hi) =>
@@ -1264,6 +1277,9 @@ object Trees {
             this(this(x, tpt), refinements)
           case AppliedTypeTree(tpt, args) =>
             this(this(x, tpt), args)
+          case TypeLambdaTree(tparams, body) =>
+            implicit val ctx: Context = localCtx
+            this(this(x, tparams), body)
           case ByNameTypeTree(result) =>
             this(x, result)
           case TypeBoundsTree(lo, hi) =>

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

@@ -21,7 +21,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   private def ta(implicit ctx: Context) = ctx.typeAssigner
 
   def Modifiers(sym: Symbol)(implicit ctx: Context): Modifiers = Modifiers(
-    sym.flags & ModifierFlags,
+    sym.flags & (if (sym.isType) ModifierFlags | VarianceFlags else ModifierFlags),
     if (sym.privateWithin.exists) sym.privateWithin.asType.name else tpnme.EMPTY,
     sym.annotations map (_.tree))
 

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

@@ -137,6 +137,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   def OrTypeTree(left: Tree, right: Tree): OrTypeTree = new OrTypeTree(left, right)
   def RefinedTypeTree(tpt: Tree, refinements: List[Tree]): RefinedTypeTree = new RefinedTypeTree(tpt, refinements)
   def AppliedTypeTree(tpt: Tree, args: List[Tree]): AppliedTypeTree = new AppliedTypeTree(tpt, args)
+  def TypeLambdaTree(tparams: List[TypeDef], body: Tree): TypeLambdaTree = new TypeLambdaTree(tparams, body)
   def ByNameTypeTree(result: Tree): ByNameTypeTree = new ByNameTypeTree(result)
   def TypeBoundsTree(lo: Tree, hi: Tree): TypeBoundsTree = new TypeBoundsTree(lo, hi)
   def Bind(name: Name, body: Tree): Bind = new Bind(name, body)

src/dotty/tools/dotc/config/Config.scala

@@ -77,6 +77,13 @@ object Config {
    */
   final val checkProjections = false
 
+  /** If this flag is set it is checked that &/| only apply to types
+   *  that are either both hk types or both * types. Should be used
+   *  only for debugging as there a generic class without arguments
+   *  can be produced in an And by Implicits.liftToClasses.
+   */
+  final val checkKinds = false
+
   /** The recursion depth for showing a summarized string */
   final val summarizeDepth = 2
 

src/dotty/tools/dotc/core/Constraint.scala

@@ -23,7 +23,7 @@ abstract class Constraint extends Showable {
   type This <: Constraint
 
   /** Does the constraint's domain contain the type parameters of `pt`? */
-  def contains(pt: PolyType): Boolean
+  def contains(pt: GenericType): Boolean
 
   /** Does the constraint's domain contain the type parameter `param`? */
   def contains(param: PolyParam): Boolean
@@ -79,7 +79,7 @@ abstract class Constraint extends Showable {
    *                 satisfiability but will solved to give instances of
    *                 type variables.
    */
-  def add(poly: PolyType, tvars: List[TypeVar])(implicit ctx: Context): This
+  def add(poly: GenericType, tvars: List[TypeVar])(implicit ctx: Context): This
 
   /** A new constraint which is derived from this constraint by updating
    *  the entry for parameter `param` to `tp`.
@@ -122,13 +122,13 @@ abstract class Constraint extends Showable {
    *                      entry array, but is going to be removed at the same step,
    *                      or -1 if no such parameter exists.
    */
-  def isRemovable(pt: PolyType, removedParam: Int = -1): Boolean
+  def isRemovable(pt: GenericType, removedParam: Int = -1): Boolean
 
   /** A new constraint with all entries coming from `pt` removed. */
-  def remove(pt: PolyType)(implicit ctx: Context): This
+  def remove(pt: GenericType)(implicit ctx: Context): This
 
   /** The polytypes constrained by this constraint */
-  def domainPolys: List[PolyType]
+  def domainPolys: List[GenericType]
 
   /** The polytype parameters constrained by this constraint */
   def domainParams: List[PolyParam]

src/dotty/tools/dotc/core/ConstraintHandling.scala

@@ -6,6 +6,7 @@ import Types._, Contexts._, Symbols._
 import Decorators._
 import config.Config
 import config.Printers._
+import TypeApplications.EtaExpansion
 import collection.mutable
 
 /** Methods for adding constraints and solving them.
@@ -193,9 +194,9 @@ trait ConstraintHandling {
     }
 
   /** The current bounds of type parameter `param` */
-  final def bounds(param: PolyParam): TypeBounds = constraint.entry(param) match {
-    case bounds: TypeBounds => bounds
-    case _ => param.binder.paramBounds(param.paramNum)
+  final def bounds(param: PolyParam): TypeBounds = {
+    val e = constraint.entry(param)
+    if (e.exists) e.bounds else param.binder.paramBounds(param.paramNum)
   }
 
   /** Add polytype `pt`, possibly with type variables `tvars`, to current constraint
@@ -293,7 +294,13 @@ trait ConstraintHandling {
         case bound: PolyParam if constraint contains bound =>
           addParamBound(bound)
         case _ =>
-          val pbound = prune(bound)
+          var pbound = prune(bound)
+          if (pbound.isHK && !param.isHK) {
+            param match {
+              case EtaExpansion(tycon) if tycon.symbol.isClass => pbound = tycon
+              case _ =>
+            }
+          }
           pbound.exists && (
             if (fromBelow) addLowerBound(param, pbound) else addUpperBound(param, pbound))
       }

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

@@ -86,17 +86,17 @@ class Definitions {
   }
 
   private def newPolyMethod(cls: ClassSymbol, name: TermName, typeParamCount: Int,
-                    resultTypeFn: PolyType => Type, flags: FlagSet = EmptyFlags) = {
+                    resultTypeFn: GenericType => Type, flags: FlagSet = EmptyFlags) = {
     val tparamNames = tpnme.syntheticTypeParamNames(typeParamCount)
     val tparamBounds = tparamNames map (_ => TypeBounds.empty)
     val ptype = PolyType(tparamNames)(_ => tparamBounds, resultTypeFn)
     newMethod(cls, name, ptype, flags)
   }
 
-  private def newT1ParameterlessMethod(cls: ClassSymbol, name: TermName, resultTypeFn: PolyType => Type, flags: FlagSet) =
+  private def newT1ParameterlessMethod(cls: ClassSymbol, name: TermName, resultTypeFn: GenericType => Type, flags: FlagSet) =
     newPolyMethod(cls, name, 1, resultTypeFn, flags)
 
-  private def newT1EmptyParamsMethod(cls: ClassSymbol, name: TermName, resultTypeFn: PolyType => Type, flags: FlagSet) =
+  private def newT1EmptyParamsMethod(cls: ClassSymbol, name: TermName, resultTypeFn: GenericType => Type, flags: FlagSet) =
     newPolyMethod(cls, name, 1, pt => MethodType(Nil, resultTypeFn(pt)), flags)
 
   private def mkArityArray(name: String, arity: Int, countFrom: Int): Array[TypeRef] = {
@@ -167,7 +167,7 @@ class Definitions {
     lazy val Any_hashCode = newMethod(AnyClass, nme.hashCode_, MethodType(Nil, IntType))
     lazy val Any_toString = newMethod(AnyClass, nme.toString_, MethodType(Nil, StringType))
     lazy val Any_##       = newMethod(AnyClass, nme.HASHHASH, ExprType(IntType), Final)
-    lazy val Any_getClass = newMethod(AnyClass, nme.getClass_, MethodType(Nil, ClassClass.typeRef), Final)
+    lazy val Any_getClass = newMethod(AnyClass, nme.getClass_, MethodType(Nil, ClassClass.typeRef.appliedTo(TypeBounds.empty)), Final)
     lazy val Any_isInstanceOf = newT1ParameterlessMethod(AnyClass, nme.isInstanceOf_, _ => BooleanType, Final)
     lazy val Any_asInstanceOf = newT1ParameterlessMethod(AnyClass, nme.asInstanceOf_, PolyParam(_, 0), Final)
 
@@ -663,71 +663,6 @@ class Definitions {
 
   def functionArity(tp: Type)(implicit ctx: Context) = tp.dealias.argInfos.length - 1
 
-  // ----- LambdaXYZ traits ------------------------------------------
-
-  private var myLambdaTraits: Set[Symbol] = Set()
-
-  /** The set of HigherKindedXYZ traits encountered so far */
-  def lambdaTraits: Set[Symbol] = myLambdaTraits
-
-  private var LambdaTraitForVariances = mutable.Map[List[Int], ClassSymbol]()
-
-  /** The HigherKinded trait corresponding to symbols `boundSyms` (which are assumed
-   *  to be the type parameters of a higher-kided type). This is a class symbol that
-   *  would be generated by the following schema.
-   *
-   *      trait LambdaXYZ extends Object with P1 with ... with Pn {
-   *        type v_1 hk$0; ...; type v_N hk$N;
-   *        type +$Apply
-   *      }
-   *
-   *  Here:
-   *
-   *   - v_i are the variances of the bound symbols (i.e. +, -, or empty).
-   *   - XYZ is a string of length N with one letter for each variant of a bound symbol,
-   *     using `P` (positive variance), `N` (negative variance), `I` (invariant).
-   *   - for each positive or negative variance v_i there is a parent trait Pj which
-   *     is the same as LambdaXYZ except that it has `I` in i-th position.
-   */
-  def LambdaTrait(vcs: List[Int]): ClassSymbol = {
-    assert(vcs.nonEmpty)
-
-    def varianceFlags(v: Int) = v match {
-      case -1 => Contravariant
-      case  0 => EmptyFlags
-      case  1 => Covariant
-    }
-
-    val completer = new LazyType  {
-      def complete(denot: SymDenotation)(implicit ctx: Context): Unit = {
-        val cls = denot.asClass.classSymbol
-        val paramDecls = newScope
-        for (i <- 0 until vcs.length)
-          newTypeParam(cls, tpnme.hkArg(i), varianceFlags(vcs(i)), paramDecls)
-        newTypeField(cls, tpnme.hkApply, Covariant, paramDecls)
-        val parentTraitRefs =
-          for (i <- 0 until vcs.length if vcs(i) != 0)
-          yield LambdaTrait(vcs.updated(i, 0)).typeRef
-        denot.info = ClassInfo(
-            ScalaPackageClass.thisType, cls, ObjectClass.typeRef :: parentTraitRefs.toList, paramDecls)
-      }
-    }
-
-    val traitName = tpnme.hkLambda(vcs)
-
-    def createTrait = {
-      val cls = newClassSymbol(
-        ScalaPackageClass,
-        traitName,
-        PureInterfaceCreationFlags | Synthetic,
-        completer)
-      myLambdaTraits += cls
-      cls
-    }
-
-    LambdaTraitForVariances.getOrElseUpdate(vcs, createTrait)
-  }
-
   // ----- primitive value class machinery ------------------------------------------
 
   /** This class would also be obviated by the implicit function type design */

src/dotty/tools/dotc/core/Denotations.scala

@@ -146,6 +146,9 @@ object Denotations {
     /** Is this denotation different from NoDenotation or an ErrorDenotation? */
     def exists: Boolean = true
 
+    /** A denotation with the info of this denotation transformed using `f` */
+    def mapInfo(f: Type => Type)(implicit ctx: Context): Denotation
+
     /** If this denotation does not exist, fallback to alternative */
     final def orElse(that: => Denotation) = if (this.exists) this else that
 
@@ -242,7 +245,7 @@ object Denotations {
       }
       else if (exists && !qualifies(symbol)) NoDenotation
       else asSingleDenotation
-     }
+    }
 
     /** Form a denotation by conjoining with denotation `that`.
      *
@@ -456,6 +459,8 @@ object Denotations {
       else if (!d2.exists) d1
       else derivedMultiDenotation(d1, d2)
     }
+    def mapInfo(f: Type => Type)(implicit ctx: Context): Denotation =
+      derivedMultiDenotation(denot1.mapInfo(f), denot2.mapInfo(f))
     def derivedMultiDenotation(d1: Denotation, d2: Denotation) =
       if ((d1 eq denot1) && (d2 eq denot2)) this else MultiDenotation(d1, d2)
     override def toString = alternatives.mkString(" <and> ")
@@ -488,6 +493,9 @@ object Denotations {
       if ((symbol eq this.symbol) && (info eq this.info)) this
       else newLikeThis(symbol, info)
 
+    def mapInfo(f: Type => Type)(implicit ctx: Context): SingleDenotation =
+      derivedSingleDenotation(symbol, f(info))
+
     def orElse(that: => SingleDenotation) = if (this.exists) this else that
 
     def altsWith(p: Symbol => Boolean): List[SingleDenotation] =
@@ -593,7 +601,8 @@ object Denotations {
      */
     private def bringForward()(implicit ctx: Context): SingleDenotation = this match {
       case denot: SymDenotation if ctx.stillValid(denot) =>
-        assert(ctx.runId > validFor.runId, s"denotation $denot invalid in run ${ctx.runId}. ValidFor: $validFor")
+        assert(ctx.runId > validFor.runId || ctx.settings.YtestPickler.value, // mixing test pickler with debug printing can travel back in time
+            s"denotation $denot invalid in run ${ctx.runId}. ValidFor: $validFor")
         var d: SingleDenotation = denot
         do {
           d.validFor = Period(ctx.period.runId, d.validFor.firstPhaseId, d.validFor.lastPhaseId)

src/dotty/tools/dotc/core/Flags.scala

@@ -436,7 +436,8 @@ object Flags {
 
   /** Flags representing modifiers that can appear in trees */
   final val ModifierFlags =
-    SourceModifierFlags | Module | Param | Synthetic | Package | Local | commonFlags(Mutable)
+    SourceModifierFlags | Module | Param | Synthetic | Package | Local |
+    commonFlags(Mutable)
       // | Trait is subsumed by commonFlags(Lazy) from SourceModifierFlags
 
   assert(ModifierFlags.isTermFlags && ModifierFlags.isTypeFlags)

src/dotty/tools/dotc/core/NameOps.scala

@@ -100,29 +100,6 @@ object NameOps {
         name.length > 0 && name.last == '=' && name.head != '=' && isOperatorPart(name.head)
     }
 
-    /** Is this the name of a higher-kinded type parameter of a Lambda? */
-    def isHkArgName =
-      name.length > 0 &&
-      name.head == tpnme.hkArgPrefixHead &&
-      name.startsWith(tpnme.hkArgPrefix) && {
-        val digits = name.drop(tpnme.hkArgPrefixLength)
-        digits.length <= 4 && digits.forall(_.isDigit)
-      }
-
-    /** The index of the higher-kinded type parameter with this name.
-     *  Pre: isLambdaArgName.
-     */
-    def hkArgIndex: Int =
-      name.drop(tpnme.hkArgPrefixLength).toString.toInt
-
-    def isLambdaTraitName(implicit ctx: Context): Boolean =
-      name.isTypeName && name.startsWith(tpnme.hkLambdaPrefix)
-
-    def lambdaTraitVariances(implicit ctx: Context): List[Int] = {
-      val vs = name.drop(tpnme.hkLambdaPrefix.length)
-      vs.toList.map(c => tpnme.varianceSuffixes.indexOf(c) - 1)
-    }
-
     /** If the name ends with $nn where nn are
       * all digits, strip the $ and the digits.
       * Otherwise return the argument.