Merge pull request #2050 from dotty-staging/drop-named-param

Drop named type parameters in classes

Author: odersky

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

@@ -253,9 +253,6 @@ trait ConstraintHandling {
     if (fromBelow && isOrType(inst) && isFullyDefined(inst) && !isOrType(upperBound))
       inst = ctx.harmonizeUnion(inst)
 
-    // 3. If instance is from below, and upper bound has open named parameters
-    //    make sure the instance has all named parameters of the bound.
-    if (fromBelow) inst = inst.widenToNamedTypeParams(param.namedTypeParams)
     inst
   }
 

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

@@ -613,9 +613,6 @@ object Flags {
   /** A private parameter accessor */
   final val PrivateParamAccessor = allOf(Private, ParamAccessor)
 
-  /** A type parameter introduced with [type ... ] */
-  final val NamedTypeParam = allOf(TypeParam, ParamAccessor)
-
   /** A local parameter */
   final val ParamAndLocal = allOf(Param, Local)
 

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

@@ -1086,9 +1086,6 @@ object SymDenotations {
     /** The type parameters of a class symbol, Nil for all other symbols */
     def typeParams(implicit ctx: Context): List[TypeSymbol] = Nil
 
-    /** The named type parameters declared or inherited by this symbol */
-    def namedTypeParams(implicit ctx: Context): Set[TypeSymbol] = Set()
-
     /** The type This(cls), where cls is this class, NoPrefix for all other symbols */
     def thisType(implicit ctx: Context): Type = NoPrefix
 
@@ -1226,11 +1223,9 @@ object SymDenotations {
     /** TODO: Document why caches are supposedly safe to use */
     private[this] var myTypeParams: List[TypeSymbol] = _
 
-    private[this] var myNamedTypeParams: Set[TypeSymbol] = _
-
     /** The type parameters in this class, in the order they appear in the current
      *  scope `decls`. This might be temporarily the incorrect order when
-     *  reading Scala2 pickled info. The problem is fixed by `updateTypeParams`
+     *  reading Scala2 pickled info. The problem is fixed by `ensureTypeParamsInCorrectOrder`,
      *  which is called once an unpickled symbol has been completed.
      */
     private def typeParamsFromDecls(implicit ctx: Context) =
@@ -1253,16 +1248,6 @@ object SymDenotations {
       myTypeParams
     }
 
-    /** The named type parameters declared or inherited by this class */
-    override final def namedTypeParams(implicit ctx: Context): Set[TypeSymbol] = {
-      def computeNamedTypeParams: Set[TypeSymbol] =
-        if (ctx.erasedTypes || is(Module)) Set() // fast return for modules to avoid scanning package decls
-        else memberNames(abstractTypeNameFilter).map(name =>
-          info.member(name).symbol.asType).filter(_.is(TypeParam, butNot = ExpandedName)).toSet
-      if (myNamedTypeParams == null) myNamedTypeParams = computeNamedTypeParams
-      myNamedTypeParams
-    }
-
     override protected[dotc] final def info_=(tp: Type) = {
       super.info_=(tp)
       myTypeParams = null // changing the info might change decls, and with it typeParams

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

@@ -246,67 +246,6 @@ class TypeApplications(val self: Type) extends AnyVal {
     case _ => Nil
   }
 
-  /** The named type parameters declared or inherited by this type.
-   *  These are all uninstantiated named type parameters of this type or one
-   *  of its base types.
-   */
-  final def namedTypeParams(implicit ctx: Context): Set[TypeSymbol] = self match {
-    case self: ClassInfo =>
-      self.cls.namedTypeParams
-    case self: RefinedType =>
-      self.parent.namedTypeParams.filterNot(_.name == self.refinedName)
-    case self: SingletonType =>
-      Set()
-    case self: TypeProxy =>
-      self.underlying.namedTypeParams
-    case _ =>
-      Set()
-  }
-
-  /** The smallest supertype of this type that instantiated none of the named type parameters
-   *  in `params`. That is, for each named type parameter `p` in `params`, either there is
-   *  no type field named `p` in this type, or `p` is a named type parameter of this type.
-   *  The first case is important for the recursive case of AndTypes, because some of their operands might
-   *  be missing the named parameter altogether, but the AndType as a whole can still
-   *  contain it.
-   */
-  final def widenToNamedTypeParams(params: Set[TypeSymbol])(implicit ctx: Context): Type = {
-
-    /** Is widening not needed for `tp`? */
-    def isOK(tp: Type) = {
-      val ownParams = tp.namedTypeParams
-      def isMissingOrOpen(param: TypeSymbol) = {
-        val ownParam = tp.nonPrivateMember(param.name).symbol
-        !ownParam.exists || ownParams.contains(ownParam.asType)
-      }
-      params.forall(isMissingOrOpen)
-    }
-
-    /** Widen type by forming the intersection of its widened parents */
-    def widenToParents(tp: Type) = {
-      val parents = tp.parents.map(p =>
-        tp.baseTypeWithArgs(p.symbol).widenToNamedTypeParams(params))
-      parents.reduceLeft(ctx.typeComparer.andType(_, _))
-    }
-
-    if (isOK(self)) self
-    else self match {
-      case self @ AppliedType(tycon, args) if !isOK(tycon) =>
-        widenToParents(self)
-      case self: TypeRef if self.symbol.isClass =>
-        widenToParents(self)
-      case self: RefinedType =>
-        val parent1 = self.parent.widenToNamedTypeParams(params)
-        if (params.exists(_.name == self.refinedName)) parent1
-        else self.derivedRefinedType(parent1, self.refinedName, self.refinedInfo)
-      case self: TypeProxy =>
-        self.superType.widenToNamedTypeParams(params)
-      case self: AndOrType =>
-        self.derivedAndOrType(
-          self.tp1.widenToNamedTypeParams(params), self.tp2.widenToNamedTypeParams(params))
-    }
-  }
-
   /** Is self type higher-kinded (i.e. of kind != "*")? */
   def isHK(implicit ctx: Context): Boolean = self.dealias match {
     case self: TypeRef => self.info.isHK

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

@@ -1264,22 +1264,10 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
     }
   }
 
-  /** `op(tp1, tp2)` unless `tp1` and `tp2` are type-constructors with at least
-   *  some unnamed type parameters.
+  /** `op(tp1, tp2)` unless `tp1` and `tp2` are type-constructors.
    *  In the latter case, combine `tp1` and `tp2` under a type lambda like this:
    *
    *    [X1, ..., Xn] -> op(tp1[X1, ..., Xn], tp2[X1, ..., Xn])
-   *
-   *  Note: There is a tension between named and positional parameters here, which
-   *  is impossible to resolve completely. Say you have
-   *
-   *    C[type T], D[type U]
-   *
-   *  Then do you expand `C & D` to `[T] -> C[T] & D[T]` or not? Under the named
-   *  type parameter interpretation, this would be wrong whereas under the traditional
-   *  higher-kinded interpretation this would be required. The problem arises from
-   *  allowing both interpretations. A possible remedy is to be somehow stricter
-   *  in where we allow which interpretation.
    */
   private def liftIfHK(tp1: Type, tp2: Type, op: (Type, Type) => Type, original: (Type, Type) => Type) = {
     val tparams1 = tp1.typeParams

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

@@ -428,16 +428,10 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
         case tp: TypeRef =>
           tp
         case tp @ RefinedType(tp1, name: TypeName, rinfo) =>
-          rinfo match {
-            case TypeAlias(TypeRef(pre, name1)) if name1 == name && (pre =:= cls.thisType) =>
-              // Don't record refinements of the form X = this.X (These can arise using named parameters).
-              typr.println(s"dropping refinement $tp")
-            case _ =>
-              val prevInfo = refinements(name)
-              refinements = refinements.updated(name,
-                if (prevInfo == null) tp.refinedInfo else prevInfo & tp.refinedInfo)
-              formals = formals.updated(name, tp1.typeParamNamed(name))
-          }
+          val prevInfo = refinements(name)
+          refinements = refinements.updated(name,
+            if (prevInfo == null) tp.refinedInfo else prevInfo & tp.refinedInfo)
+          formals = formals.updated(name, tp1.typeParamNamed(name))
           normalizeToRef(tp1)
         case _: ErrorType =>
           defn.AnyType

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

@@ -549,13 +549,7 @@ object Types {
 
       def goThis(tp: ThisType) = {
         val d = go(tp.underlying)
-        if (d.exists)
-          if ((pre eq tp) && d.symbol.is(NamedTypeParam) && (d.symbol.owner eq tp.cls))
-            // If we look for a named type parameter `P` in `C.this.P`, looking up
-            // the fully applied self type of `C` will give as an info the alias type
-            // `P = this.P`. We need to return a denotation with the underlying bounds instead.
-            d.symbol.denot
-          else d
+        if (d.exists) d
         else
           // There is a special case to handle:
           //   trait Super { this: Sub => private class Inner {} println(this.Inner) }

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

@@ -805,7 +805,7 @@ object Parsers {
     private def simpleTypeRest(t: Tree): Tree = in.token match {
       case HASH => simpleTypeRest(typeProjection(t))
       case LBRACKET => simpleTypeRest(atPos(startOffset(t)) {
-        AppliedTypeTree(t, typeArgs(namedOK = true, wildOK = true)) })
+        AppliedTypeTree(t, typeArgs(namedOK = false, wildOK = true)) })
       case _ => t
     }
 
@@ -1664,7 +1664,7 @@ object Parsers {
  /* -------- PARAMETERS ------------------------------------------- */
 
     /** ClsTypeParamClause::=  `[' ClsTypeParam {`,' ClsTypeParam} `]'
-     *  ClsTypeParam      ::=  {Annotation} [{Modifier} type] [`+' | `-']
+     *  ClsTypeParam      ::=  {Annotation} [`+' | `-']
      *                         id [HkTypeParamClause] TypeParamBounds
      *
      *  DefTypeParamClause::=  `[' DefTypeParam {`,' DefTypeParam} `]'
@@ -1680,25 +1680,17 @@ object Parsers {
       def typeParam(): TypeDef = {
         val isConcreteOwner = ownerKind == ParamOwner.Class || ownerKind == ParamOwner.Def
         val start = in.offset
-        var mods = annotsAsMods()
-        if (ownerKind == ParamOwner.Class) {
-          mods = modifiers(start = mods)
-          mods =
-            atPos(start, in.offset) {
-              if (in.token == TYPE) {
-                val mod = atPos(in.skipToken()) { Mod.Type() }
-                (mods | Param | ParamAccessor).withAddedMod(mod)
-              } else {
-                if (mods.hasFlags) syntaxError(TypeParamsTypeExpected(mods, ident()))
-                mods | Param | PrivateLocal
-              }
-            }
-        }
-        else mods = atPos(start) (mods | Param)
-        if (ownerKind != ParamOwner.Def) {
-          if (isIdent(nme.raw.PLUS)) mods |= Covariant
-          else if (isIdent(nme.raw.MINUS)) mods |= Contravariant
-          if (mods is VarianceFlags) in.nextToken()
+        val mods = atPos(start) {
+          annotsAsMods() | {
+            if (ownerKind == ParamOwner.Class) Param | PrivateLocal
+            else Param
+          } | {
+            if (ownerKind != ParamOwner.Def)
+              if (isIdent(nme.raw.PLUS)) { in.nextToken(); Covariant }
+              else if (isIdent(nme.raw.MINUS)) { in.nextToken(); Contravariant }
+              else EmptyFlags
+            else EmptyFlags
+          }
         }
         atPos(start, nameStart) {
           val name =

compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java

@@ -32,7 +32,6 @@ public enum ErrorMessageID {
     ByNameParameterNotSupportedID,
     WrongNumberOfTypeArgsID,
     IllegalVariableInPatternAlternativeID,
-    TypeParamsTypeExpectedID,
     IdentifierExpectedID,
     AuxConstructorNeedsNonImplicitParameterID,
     IncorrectRepeatedParameterSyntaxID,

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -691,19 +691,6 @@ object messages {
     }
   }
 
-  case class TypeParamsTypeExpected(mods: untpd.Modifiers, identifier: TermName)(implicit ctx: Context)
-  extends Message(TypeParamsTypeExpectedID) {
-    val kind = "Syntax"
-    val msg = hl"""Expected ${"type"} keyword for type parameter $identifier"""
-    val explanation =
-      hl"""|This happens when you add modifiers like ${"private"} or ${"protected"}
-           |to your type parameter definition without adding the ${"type"} keyword.
-           |
-           |Add ${"type"} to your code, e.g.:
-           |${s"trait A[${mods.flags} type $identifier]"}
-           |"""
-  }
-
   case class IdentifierExpected(identifier: String)(implicit ctx: Context)
   extends Message(IdentifierExpectedID) {
     val kind = "Syntax"
@@ -1138,7 +1125,7 @@ object messages {
            |
            |You may want to create an anonymous class extending ${cls.name} with
            |  ${s"class ${cls.name} { }"}
-           |  
+           |
            |or add a companion object with
            |  ${s"object ${cls.name} extends ${cls.name}"}
            |

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

@@ -753,11 +753,10 @@ class Namer { typer: Typer =>
       /* Check parent type tree `parent` for the following well-formedness conditions:
        * (1) It must be a class type with a stable prefix (@see checkClassTypeWithStablePrefix)
        * (2) If may not derive from itself
-       * (3) Overriding type parameters must be correctly forwarded. (@see checkTypeParamOverride)
-       * (4) The class is not final
-       * (5) If the class is sealed, it is defined in the same compilation unit as the current class
+       * (3) The class is not final
+       * (4) If the class is sealed, it is defined in the same compilation unit as the current class
        */
-      def checkedParentType(parent: untpd.Tree, paramAccessors: List[Symbol]): Type = {
+      def checkedParentType(parent: untpd.Tree): Type = {
         val ptype = parentType(parent)(ctx.superCallContext)
         if (cls.isRefinementClass) ptype
         else {
@@ -772,8 +771,6 @@ class Namer { typer: Typer =>
             ctx.error(i"cyclic inheritance: $cls extends itself$addendum", parent.pos)
             defn.ObjectType
           }
-          else if (!paramAccessors.forall(checkTypeParamOverride(pt, _)))
-            defn.ObjectType
           else {
             val pclazz = pt.typeSymbol
             if (pclazz.is(Final))
@@ -785,47 +782,7 @@ class Namer { typer: Typer =>
         }
       }
 
-      /* Check that every parameter with the same name as a visible named parameter in the parent
-       * class satisfies the following two conditions:
-       *  (1) The overriding parameter is also named (i.e. not local/name mangled).
-       *  (2) The overriding parameter is passed on directly to the parent parameter, or the
-       *      parent parameter is not fully defined.
-       * @return true if conditions are satisfied, false otherwise.
-       */
-      def checkTypeParamOverride(parent: Type, paramAccessor: Symbol): Boolean = {
-        var ok = true
-        val pname = paramAccessor.name
-
-        def illegal(how: String): Unit = {
-          ctx.error(em"Illegal override of public type parameter $pname in $parent$how", paramAccessor.pos)
-          ok = false
-        }
-
-        def checkAlias(tp: Type): Unit = tp match {
-          case tp: RefinedType =>
-            if (tp.refinedName == pname)
-              tp.refinedInfo match {
-                case TypeAlias(alias) =>
-                  alias match {
-                    case TypeRef(pre, name1) if name1 == pname && (pre =:= cls.thisType) =>
-                      // OK, parameter is passed on directly
-                    case _ =>
-                      illegal(em".\nParameter is both redeclared and instantiated with $alias.")
-                  }
-                case _ => // OK, argument is not fully defined
-              }
-            else checkAlias(tp.parent)
-          case _ =>
-        }
-        if (parent.nonPrivateMember(paramAccessor.name).symbol.is(Param))
-          if (paramAccessor is Private)
-            illegal("\nwith private parameter. Parameter definition needs to be prefixed with `type'.")
-          else
-            checkAlias(parent)
-        ok
-      }
-
-      addAnnotations(denot.symbol, original)
+     addAnnotations(denot.symbol, original)
 
       val selfInfo =
         if (self.isEmpty) NoType
@@ -853,8 +810,7 @@ class Namer { typer: Typer =>
 
       indexAndAnnotate(rest)(inClassContext(selfInfo))
 
-      val tparamAccessors = decls.filter(_ is TypeParamAccessor).toList
-      val parentTypes = ensureFirstIsClass(parents.map(checkedParentType(_, tparamAccessors)))
+      val parentTypes = ensureFirstIsClass(parents.map(checkedParentType(_)))
       val parentRefs = ctx.normalizeToClassRefs(parentTypes, cls, decls)
       typr.println(s"completing $denot, parents = $parents, parentTypes = $parentTypes, parentRefs = $parentRefs")
 

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

@@ -241,8 +241,6 @@ object RefChecks {
           isDefaultGetter(member.name) || // default getters are not checked for compatibility
           memberTp.overrides(otherTp)
 
-      def domain(sym: Symbol): Set[Name] = sym.info.namedTypeParams.map(_.name)
-
       //Console.println(infoString(member) + " overrides " + infoString(other) + " in " + clazz);//DEBUG
 
       // return if we already checked this combination elsewhere
@@ -344,9 +342,6 @@ object RefChecks {
         overrideError("cannot be used here - only term macros can override term macros")
       } else if (!compatibleTypes) {
         overrideError("has incompatible type" + err.whyNoMatchStr(memberTp, otherTp))
-      } else if (member.isType && domain(member) != domain(other)) {
-        overrideError("has different named type parameters: "+
-             i"[${domain(member).toList}%, %] instead of [${domain(other).toList}%, %]")
       } else {
         checkOverrideDeprecated()
       }