Drop support of sealed modifier on type parameters

Author: odersky

compiler/src/dotty/tools/dotc/cc/CaptureOps.scala

@@ -198,12 +198,6 @@ extension (tp: Type)
     case _: TypeRef | _: AppliedType => tp.typeSymbol.hasAnnotation(defn.CapabilityAnnot)
     case _ => false
 
-  def isSealed(using Context): Boolean = tp match
-    case tp: TypeParamRef => tp.underlying.isSealed
-    case tp: TypeBounds => tp.hi.hasAnnotation(defn.Caps_SealedAnnot)
-    case tp: TypeRef => tp.symbol.is(Sealed) || tp.info.isSealed // TODO: drop symbol flag?
-    case _ => false
-
   /** Drop @retains annotations everywhere */
   def dropAllRetains(using Context): Type = // TODO we should drop retains from inferred types before unpickling
     val tm = new TypeMap:

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

@@ -993,7 +993,6 @@ class Definitions {
     @tu lazy val Caps_unsafeBox: Symbol = CapsUnsafeModule.requiredMethod("unsafeBox")
     @tu lazy val Caps_unsafeUnbox: Symbol = CapsUnsafeModule.requiredMethod("unsafeUnbox")
     @tu lazy val Caps_unsafeBoxFunArg: Symbol = CapsUnsafeModule.requiredMethod("unsafeBoxFunArg")
-    @tu lazy val Caps_SealedAnnot: ClassSymbol = requiredClass("scala.caps.Sealed")
     @tu lazy val expandedUniversalSet: CaptureSet = CaptureSet(captureRoot.termRef)
 
   @tu lazy val PureClass: Symbol = requiredClass("scala.Pure")

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

@@ -4072,15 +4072,10 @@ object Types {
 
     protected def toPInfo(tp: Type)(using Context): PInfo
 
-    /** If `tparam` is a sealed type parameter symbol of a polymorphic method, add
-     *  a @caps.Sealed annotation to the upperbound in `tp`.
-     */
-    protected def addSealed(tparam: ParamInfo, tp: Type)(using Context): Type = tp
-
     def fromParams[PI <: ParamInfo.Of[N]](params: List[PI], resultType: Type)(using Context): Type =
       if (params.isEmpty) resultType
       else apply(params.map(_.paramName))(
-        tl => params.map(param => toPInfo(addSealed(param, tl.integrate(params, param.paramInfo)))),
+        tl => params.map(param => toPInfo(tl.integrate(params, param.paramInfo))),
         tl => tl.integrate(params, resultType))
   }
 
@@ -4402,16 +4397,6 @@ object Types {
         resultTypeExp: PolyType => Type)(using Context): PolyType =
       unique(new PolyType(paramNames)(paramInfosExp, resultTypeExp))
 
-    override protected def addSealed(tparam: ParamInfo, tp: Type)(using Context): Type =
-      tparam match
-        case tparam: Symbol if tparam.is(Sealed) =>
-          tp match
-            case tp @ TypeBounds(lo, hi) =>
-              tp.derivedTypeBounds(lo,
-                AnnotatedType(hi, Annotation(defn.Caps_SealedAnnot, tparam.span)))
-            case _ => tp
-        case _ => tp
-
     def unapply(tl: PolyType): Some[(List[LambdaParam], Type)] =
       Some((tl.typeParams, tl.resType))
   }

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

@@ -3266,9 +3266,6 @@ object Parsers {
         val start = in.offset
         var mods = annotsAsMods() | Param
         if ownerKind == ParamOwner.Class then mods |= PrivateLocal
-        if Feature.ccEnabled && in.token == SEALED then
-          mods |= Sealed
-          in.nextToken()
         if isIdent(nme.raw.PLUS) && checkVarianceOK() then
           mods |= Covariant
         else if isIdent(nme.raw.MINUS) && checkVarianceOK() then

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

@@ -519,11 +519,7 @@ object Checking {
         // but they can never be one of ClassOnlyFlags
     if !sym.isClass && sym.isOneOf(ClassOnlyFlags) then
       val illegal = sym.flags & ClassOnlyFlags
-      if sym.is(TypeParam)
-          && illegal == Sealed
-          && Feature.ccEnabled && cc.ccConfig.allowUniversalInBoxed
-      then () // OK
-      else fail(em"only classes can be ${illegal.flagsString}")
+      fail(em"only classes can be ${illegal.flagsString}")
     if (sym.is(AbsOverride) && !sym.owner.is(Trait))
       fail(AbstractOverrideOnlyInTraits(sym))
     if sym.is(Trait) then

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

@@ -1042,14 +1042,7 @@ class Namer { typer: Typer =>
           tp
 
       val rhs1 = typedAheadType(rhs)
-      val rhsBodyType: TypeBounds =
-        val bounds = addVariances(rhs1.tpe).toBounds
-        if sym.is(Sealed) then
-          sym.resetFlag(Sealed)
-          bounds.derivedTypeBounds(bounds.lo,
-            AnnotatedType(bounds.hi, Annotation(defn.Caps_SealedAnnot, rhs1.span)))
-        else bounds
-
+      val rhsBodyType: TypeBounds = addVariances(rhs1.tpe).toBounds
       val unsafeInfo = if (isDerived) rhsBodyType else abstracted(rhsBodyType)
 
       def opaqueToBounds(info: Type): Type =

library/src/scala/caps.scala

@@ -44,9 +44,3 @@ import annotation.experimental
       def unsafeBoxFunArg: T => U = f
 
   end unsafe
-
-  /** An annotation that expresses the sealed modifier on a type parameter
-   *  Should not be directly referred to in source
-   */
-  @deprecated("The Sealed annotation should not be directly used in source code.\nUse the `sealed` modifier on type parameters instead.")
-  class Sealed extends annotation.Annotation

tests/pos-special/stdlib/collection/ArrayOps.scala

@@ -121,7 +121,7 @@ object ArrayOps {
   }
 
   @SerialVersionUID(3L)
-  private[collection] final class ArrayIterator[@specialized(Specializable.Everything) sealed A](xs: Array[A]) extends AbstractIterator[A] with Serializable {
+  private[collection] final class ArrayIterator[@specialized(Specializable.Everything) A](xs: Array[A]) extends AbstractIterator[A] with Serializable {
     private[this] var pos = 0
     private[this] val len = xs.length
     override def knownSize: Int = len - pos
@@ -144,7 +144,7 @@ object ArrayOps {
   }
 
   @SerialVersionUID(3L)
-  private final class ReverseIterator[@specialized(Specializable.Everything) sealed A](xs: Array[A]) extends AbstractIterator[A] with Serializable {
+  private final class ReverseIterator[@specialized(Specializable.Everything) A](xs: Array[A]) extends AbstractIterator[A] with Serializable {
     private[this] var pos = xs.length-1
     def hasNext: Boolean = pos >= 0
     def next(): A = {
@@ -777,7 +777,7 @@ final class ArrayOps[A](private val xs: Array[A]) extends AnyVal {
     *           Returns `z` if this array is empty.
     */
   def foldLeft[B](z: B)(op: (B, A) => B): B = {
-    def f[@specialized(Specializable.Everything) sealed T](xs: Array[T], op: (Any, Any) => Any, z: Any): Any = {
+    def f[@specialized(Specializable.Everything) T](xs: Array[T], op: (Any, Any) => Any, z: Any): Any = {
       val length = xs.length
       var v: Any = z
       var i = 0
@@ -883,7 +883,7 @@ final class ArrayOps[A](private val xs: Array[A]) extends AnyVal {
     *           Returns `z` if this array is empty.
     */
   def foldRight[B](z: B)(op: (A, B) => B): B = {
-    def f[@specialized(Specializable.Everything) sealed T](xs: Array[T], op: (Any, Any) => Any, z: Any): Any = {
+    def f[@specialized(Specializable.Everything) T](xs: Array[T], op: (Any, Any) => Any, z: Any): Any = {
       var v = z
       var i = xs.length - 1
       while(i >= 0) {