Various fixes to stdlib-cc (#19873)

fixes #19819, fixes #19652, fixes #19847, supersedes #19858

compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -242,10 +242,12 @@ class PlainPrinter(_ctx: Context) extends Printer {
         val refsText = if showAsCap then rootSetText else toTextCaptureSet(refs)
         toTextCapturing(parent, refsText, boxText)
       case tp @ RetainingType(parent, refs) =>
-        val refsText = refs match
-          case ref :: Nil if ref.symbol == defn.captureRoot => rootSetText
-          case _ => toTextRetainedElems(refs)
-        toTextCapturing(parent, refsText, "") ~ Str("R").provided(printDebug)
+        if Feature.ccEnabledSomewhere then
+          val refsText = refs match
+            case ref :: Nil if ref.symbol == defn.captureRoot => rootSetText
+            case _ => toTextRetainedElems(refs)
+          toTextCapturing(parent, refsText, "") ~ Str("R").provided(printDebug)
+        else toText(parent)
       case tp: PreviousErrorType if ctx.settings.XprintTypes.value =>
         "<error>" // do not print previously reported error message because they may try to print this error type again recuresevely
       case tp: ErrorType =>

scala2-library-cc/src/scala/collection/Seq.scala

@@ -206,7 +206,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any with SeqViewOps[A, CC, C] { self =>
     *
     * @return a new $coll consisting of all the elements of this $coll without duplicates.
     */
-  def distinct: C = distinctBy(identity)
+  override def distinct: C = distinctBy(identity)
 
   /** Selects all the elements of this $coll ignoring the duplicates as determined by `==` after applying
     * the transforming function `f`.
@@ -215,7 +215,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any with SeqViewOps[A, CC, C] { self =>
     * @tparam B the type of the elements after being transformed by `f`
     * @return a new $coll consisting of all the elements of this $coll without duplicates.
     */
-  def distinctBy[B](f: A -> B): C = fromSpecific(new View.DistinctBy(this, f))
+  override def distinctBy[B](f: A -> B): C = fromSpecific(new View.DistinctBy(this, f))
 
   /** Returns new $coll with elements in reversed order.
    *
@@ -293,7 +293,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any with SeqViewOps[A, CC, C] { self =>
    *          all elements of this $coll followed by the minimal number of occurrences of `elem` so
    *          that the resulting collection has a length of at least `len`.
    */
-  def padTo[B >: A](len: Int, elem: B): CC[B] = iterableFactory.from(new View.PadTo(this, len, elem))
+  override def padTo[B >: A](len: Int, elem: B): CC[B] = iterableFactory.from(new View.PadTo(this, len, elem))
 
   /** Computes the length of the longest segment that starts from the first element
     *  and whose elements all satisfy some predicate.
@@ -544,7 +544,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any with SeqViewOps[A, CC, C] { self =>
    *    // List(b, b, a)
    *  }}}
    */
-  def permutations: Iterator[C] =
+  override def permutations: Iterator[C] =
     if (isEmpty) Iterator.single(coll)
     else new PermutationsItr
 
@@ -585,7 +585,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any with SeqViewOps[A, CC, C] { self =>
    *    // List(b, a)
    *  }}}
    */
-  def combinations(n: Int): Iterator[C] =
+  override def combinations(n: Int): Iterator[C] =
     if (n < 0 || n > size) Iterator.empty
     else new CombinationsItr(n)
 
@@ -759,7 +759,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any with SeqViewOps[A, CC, C] { self =>
    *    List("Bobby", "Bob", "John", "Steve", "Tom")
    *  }}}
    */
-  def sortWith(lt: (A, A) => Boolean): C = sorted(Ordering.fromLessThan(lt))
+  override def sortWith(lt: (A, A) => Boolean): C = sorted(Ordering.fromLessThan(lt))
 
   /** Sorts this $coll according to the Ordering which results from transforming
     * an implicitly given Ordering with a transformation function.
@@ -786,7 +786,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any with SeqViewOps[A, CC, C] { self =>
     *    res0: Array[String] = Array(The, dog, fox, the, lazy, over, brown, quick, jumped)
     *  }}}
     */
-  def sortBy[B](f: A => B)(implicit ord: Ordering[B]): C = sorted(ord on f)
+  override def sortBy[B](f: A => B)(implicit ord: Ordering[B]): C = sorted(ord on f)
 
   /** Produces the range of all indices of this sequence.
     * $willForceEvaluation
@@ -944,7 +944,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any with SeqViewOps[A, CC, C] { self =>
     *                   except that `replaced` elements starting from `from` are replaced
     *                   by all the elements of `other`.
     */
-  def patch[B >: A](from: Int, other: IterableOnce[B]^, replaced: Int): CC[B] =
+  override def patch[B >: A](from: Int, other: IterableOnce[B]^, replaced: Int): CC[B] =
     iterableFactory.from(new View.Patched(this, from, other, replaced))
       .unsafeAssumePure // assume pure OK since iterableFactory.from is eager for Seq
 
@@ -957,7 +957,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any with SeqViewOps[A, CC, C] { self =>
     *                                    lazy collection this exception may be thrown at a later time or not at
     *                                    all (if the end of the collection is never evaluated).
     */
-  def updated[B >: A](index: Int, elem: B): CC[B] = {
+  override def updated[B >: A](index: Int, elem: B): CC[B] = {
     if(index < 0) throw new IndexOutOfBoundsException(index.toString)
     val k = knownSize
     if(k >= 0 && index >= k) throw new IndexOutOfBoundsException(index.toString)

scala2-library-cc/src/scala/collection/SeqView.scala

@@ -30,11 +30,43 @@ trait SeqViewOps[+A, +CC[_], +C] extends Any with IterableOps[A, CC, C] {
   def length: Int
   def apply(x: Int): A
   def appended[B >: A](elem: B): CC[B]^{this}
-  def updated[B >: A](index: Int, elem: B): CC[B]^{this}
   def prepended[B >: A](elem: B): CC[B]^{this}
   def reverse: C^{this}
   def sorted[B >: A](implicit ord: Ordering[B]): C^{this}
 
+  // Placeholder implementations for the corresponding methods in SeqOps.
+  // This is needed due to the change in the class hierarchy in cc stdlib.
+  // See #19660 and #19819.
+  // -------------------
+  def updated[B >: A](index: Int, elem: B): CC[B]^{this} =
+    assert(false, "This is a placeholder implementation in the capture checked Scala 2 library.")
+    ???
+  def padTo[B >: A](len: Int, elem: B): CC[B]^{this} =
+    assert(false, "This is a placeholder implementation in the capture checked Scala 2 library.")
+    ???
+  def patch[B >: A](from: Int, other: IterableOnce[B]^, replaced: Int): CC[B]^{this, other} =
+    assert(false, "This is a placeholder implementation in the capture checked Scala 2 library.")
+    ???
+  def combinations(n: Int): Iterator[C^{this}]^{this} =
+    assert(false, "This is a placeholder implementation in the capture checked Scala 2 library.")
+    ???
+  def sortBy[B](f: A => B)(implicit ord: Ordering[B]): C^{this, f} =
+    assert(false, "This is a placeholder implementation in the capture checked Scala 2 library.")
+    ???
+  def sortWith(lt: (A, A) => Boolean): C^{this, lt} =
+    assert(false, "This is a placeholder implementation in the capture checked Scala 2 library.")
+    ???
+  def permutations: Iterator[C^{this}]^{this} =
+    assert(false, "This is a placeholder implementation in the capture checked Scala 2 library.")
+    ???
+  def distinct: C^{this} =
+    assert(false, "This is a placeholder implementation in the capture checked Scala 2 library.")
+    ???
+  def distinctBy[B](f: A -> B): C^{this} =
+    assert(false, "This is a placeholder implementation in the capture checked Scala 2 library.")
+    ???
+  // -------------------
+
   def reverseIterator: Iterator[A]^{this} = reversed.iterator
 }
 
@@ -46,15 +78,6 @@ trait SeqView[+A] extends SeqViewOps[A, View, View[A]] with View[A] {
   override def map[B](f: A => B): SeqView[B]^{this, f} = new SeqView.Map(this, f)
   override def appended[B >: A](elem: B): SeqView[B]^{this} = new SeqView.Appended(this, elem)
 
-  // Copied from SeqOps. This is needed due to the change of class hierarchy in stdlib.
-  // See #19660.
-  override def updated[B >: A](index: Int, elem: B): View[B]^{this} = {
-    if(index < 0) throw new IndexOutOfBoundsException(index.toString)
-    val k = knownSize
-    if(k >= 0 && index >= k) throw new IndexOutOfBoundsException(index.toString)
-    iterableFactory.from(new View.Updated(this, index, elem))
-  }
-
   override def prepended[B >: A](elem: B): SeqView[B]^{this} = new SeqView.Prepended(elem, this)
   override def reverse: SeqView[A]^{this} = new SeqView.Reverse(this)
   override def take(n: Int): SeqView[A]^{this} = new SeqView.Take(this, n)

scala2-library-cc/src/scala/collection/generic/IsSeq.scala

@@ -54,24 +54,22 @@ object IsSeq {
     seqOpsIsSeqVal.asInstanceOf[IsSeq[CC0[A0]] { type A = A0; type C = CC0[A0] }]
 
   /** !!! Under cc, views are not Seqs and can't use SeqOps.
-   *  So this should be renamed to seqViewIsIterable
-   */
-  implicit def seqViewIsSeq[CC0[X] <: SeqView[X], A0]: IsIterable[CC0[A0]] { type A = A0; type C = View[A0] } =
-    new IsIterable[CC0[A0]] {
-      type A = A0
-      type C = View[A]
-      def apply(coll: CC0[A0]): IterableOps[A0, View, View[A0]] = coll
-    }
+    * Therefore, [[seqViewIsSeq]] now returns an [[IsIterable]].
+    * The helper method [[seqViewIsSeq_]] is added to make the binary compatible.
+    */
+  @annotation.targetName("seqViewIsSeq")
+  @annotation.publicInBinary
+  private[IsSeq] def seqViewIsSeq_[CC0[X] <: SeqView[X], A0]: IsSeq[CC0[A0]] { type A = A0; type C = View[A0] } = ???
+  implicit inline def seqViewIsSeq[CC0[X] <: SeqView[X], A0]: IsIterable[CC0[A0]] { type A = A0; type C = View[A0] } = seqViewIsSeq_[CC0, A0].asInstanceOf
 
   /** !!! Under cc, views are not Seqs and can't use SeqOps.
-   *  So this should be renamed to stringViewIsIterable
-   */
-  implicit val stringViewIsSeq: IsIterable[StringView] { type A = Char; type C = View[Char] } =
-    new IsIterable[StringView] {
-      type A = Char
-      type C = View[Char]
-      def apply(coll: StringView): IterableOps[Char, View, View[Char]] = coll
-    }
+    * Therefore, [[stringViewIsSeq]] now returns an [[IsIterable]].
+    * The helper method [[stringViewIsSeq__]] is added to make the binary compatible.
+    */
+  @annotation.targetName("stringViewIsSeq")
+  @annotation.publicInBinary
+  private[IsSeq] val stringViewIsSeq_ : IsSeq[StringView] { type A = Char; type C = View[Char] } = ???
+  inline implicit def stringViewIsSeq: IsIterable[StringView] { type A = Char; type C = View[Char] } = stringViewIsSeq_.asInstanceOf
 
   implicit val stringIsSeq: IsSeq[String] { type A = Char; type C = String } =
     new IsSeq[String] {

tests/run/enrich-gentraversable.scala

@@ -3,6 +3,7 @@ import scala.language.postfixOps
 
 object Test extends App {
   import scala.collection.generic.IsIterable
+  import scala.collection.generic.IsSeq.seqViewIsSeq
   import scala.collection.{BuildFrom, Iterable, IterableOps, View}
   import scala.collection.immutable.TreeMap