Fixes to capture annotations in stdlib

These problems were discovered once we started recording uses of this references.
The recording is not yet part of this commit because it requires downstream bugfixes
in the compiler.

Author: odersky

library/src/scala/collection/Iterator.scala

@@ -418,7 +418,7 @@ trait Iterator[+A] extends IterableOnce[A] with IterableOnceOps[A, Iterator, Ite
 
   @deprecated("Call scanRight on an Iterable instead.", "2.13.0")
   def scanRight[B](z: B)(op: (A, B) => B): Iterator[B]^{this, op} = ArrayBuffer.from(this).scanRight(z)(op).iterator
- 
+
   /** Finds index of the first element satisfying some predicate after or at some start index.
     *
     *  $mayNotTerminateInf
@@ -494,9 +494,9 @@ trait Iterator[+A] extends IterableOnce[A] with IterableOnceOps[A, Iterator, Ite
       while (p(hd) == isFlipped) {
         if (!self.hasNext) return false
         hd = self.next()
-      } 
+      }
       hdDefined = true
-      true 
+      true
     }
 
     def next() =
@@ -874,7 +874,7 @@ trait Iterator[+A] extends IterableOnce[A] with IterableOnceOps[A, Iterator, Ite
     */
   def duplicate: (Iterator[A]^{this}, Iterator[A]^{this}) = {
     val gap = new scala.collection.mutable.Queue[A]
-    var ahead: Iterator[A] = null
+    var ahead: Iterator[A]^ = null
     class Partner extends AbstractIterator[A] {
       override def knownSize: Int = self.synchronized {
         val thisSize = self.knownSize
@@ -890,7 +890,7 @@ trait Iterator[+A] extends IterableOnce[A] with IterableOnceOps[A, Iterator, Ite
         if (gap.isEmpty) ahead = this
         if (this eq ahead) {
           val e = self.next()
-          gap enqueue e
+          gap.enqueue(e)
           e
         } else gap.dequeue()
       }
@@ -918,7 +918,7 @@ trait Iterator[+A] extends IterableOnce[A] with IterableOnceOps[A, Iterator, Ite
     */
   def patch[B >: A](from: Int, patchElems: Iterator[B]^, replaced: Int): Iterator[B]^{this, patchElems} =
     new AbstractIterator[B] {
-      private[this] var origElems = self
+      private[this] var origElems: Iterator[B]^ = self
       // > 0  => that many more elems from `origElems` before switching to `patchElems`
       //   0  => need to drop elems from `origElems` and start using `patchElems`
       //  -1  => have dropped elems from `origElems`, will be using `patchElems` until it's empty

library/src/scala/collection/LazyZipOps.scala

@@ -389,7 +389,7 @@ final class LazyZip4[+El1, +El2, +El3, +El4, C1] private[collection](src: C1,
   }
 
   private def toIterable: View[(El1, El2, El3, El4)]^{this} = new AbstractView[(El1, El2, El3, El4)] {
-    def iterator: AbstractIterator[(El1, El2, El3, El4)] = new AbstractIterator[(El1, El2, El3, El4)] {
+    def iterator: AbstractIterator[(El1, El2, El3, El4)]^{this} = new AbstractIterator[(El1, El2, El3, El4)] {
       private[this] val elems1 = coll1.iterator
       private[this] val elems2 = coll2.iterator
       private[this] val elems3 = coll3.iterator

library/src/scala/collection/SeqView.scala

@@ -202,10 +202,10 @@ object SeqView {
     override def knownSize: Int = len
     override def isEmpty: Boolean = len == 0
     override def to[C1](factory: Factory[A, C1]): C1 = _sorted.to(factory)
-    override def reverse: SeqView[A] = new ReverseSorted
+    override def reverse: SeqView[A]^{this} = new ReverseSorted
     // we know `_sorted` is either tiny or has efficient random access,
     //  so this is acceptable for `reversed`
-    override protected def reversed: Iterable[A] = new ReverseSorted
+    override protected def reversed: Iterable[A]^{this} = new ReverseSorted
 
     override def sorted[B1 >: A](implicit ord1: Ordering[B1]): SeqView[A]^{this} =
       if (ord1 == this.ord) this

library/src/scala/collection/Stepper.scala

@@ -260,7 +260,7 @@ trait IntStepper extends Stepper[Int] {
 
   def spliterator[B >: Int]: Spliterator.OfInt^{this} = new IntStepper.IntStepperSpliterator(this)
 
-  def javaIterator[B >: Int]: PrimitiveIterator.OfInt = new PrimitiveIterator.OfInt {
+  def javaIterator[B >: Int]: PrimitiveIterator.OfInt^{this} = new PrimitiveIterator.OfInt {
     def hasNext: Boolean = hasStep
     def nextInt(): Int = nextStep()
   }
@@ -298,7 +298,7 @@ trait DoubleStepper extends Stepper[Double] {
 
   def spliterator[B >: Double]: Spliterator.OfDouble^{this} = new DoubleStepper.DoubleStepperSpliterator(this)
 
-  def javaIterator[B >: Double]: PrimitiveIterator.OfDouble = new PrimitiveIterator.OfDouble {
+  def javaIterator[B >: Double]: PrimitiveIterator.OfDouble^{this} = new PrimitiveIterator.OfDouble {
     def hasNext: Boolean = hasStep
     def nextDouble(): Double = nextStep()
   }
@@ -337,7 +337,7 @@ trait LongStepper extends Stepper[Long] {
 
   def spliterator[B >: Long]: Spliterator.OfLong^{this} = new LongStepper.LongStepperSpliterator(this)
 
-  def javaIterator[B >: Long]: PrimitiveIterator.OfLong = new PrimitiveIterator.OfLong {
+  def javaIterator[B >: Long]: PrimitiveIterator.OfLong^{this} = new PrimitiveIterator.OfLong {
     def hasNext: Boolean = hasStep
     def nextLong(): Long = nextStep()
   }

library/src/scala/collection/View.scala

@@ -172,7 +172,7 @@ object View extends IterableFactory[View] {
 
   @SerialVersionUID(3L)
   class LeftPartitionMapped[A, A1, A2](underlying: SomeIterableOps[A]^, f: A => Either[A1, A2]) extends AbstractView[A1] {
-    def iterator: AbstractIterator[A1] = new AbstractIterator[A1] {
+    def iterator: AbstractIterator[A1]^{this} = new AbstractIterator[A1] {
       private[this] val self = underlying.iterator
       private[this] var hd: A1 = _
       private[this] var hdDefined: Boolean = false
@@ -197,7 +197,7 @@ object View extends IterableFactory[View] {
 
   @SerialVersionUID(3L)
   class RightPartitionMapped[A, A1, A2](underlying: SomeIterableOps[A]^, f: A => Either[A1, A2]) extends AbstractView[A2] {
-      def iterator: AbstractIterator[A2] = new AbstractIterator[A2] {
+      def iterator: AbstractIterator[A2]^{this} = new AbstractIterator[A2] {
         private[this] val self = underlying.iterator
         private[this] var hd: A2 = _
         private[this] var hdDefined: Boolean = false

library/src/scala/collection/convert/StreamExtensions.scala

@@ -30,6 +30,7 @@ import scala.jdk._
   * [[scala.jdk.javaapi.StreamConverters]].
   */
 trait StreamExtensions {
+  this: StreamExtensions =>
   // collections
 
   implicit class IterableHasSeqStream[A](cc: IterableOnce[A]) {

library/src/scala/collection/mutable/HashTable.scala

@@ -211,7 +211,7 @@ private[collection] trait HashTable[A, B, Entry >: Null <: HashEntry[A, Entry]]
 
   /** An iterator returning all entries.
    */
-  def entriesIterator: Iterator[Entry] = new AbstractIterator[Entry] {
+  def entriesIterator: Iterator[Entry]^{this} = new AbstractIterator[Entry] {
     val iterTable = table
     var idx       = lastPopulatedIndex
     var es        = iterTable(idx)

tests/run-custom-args/captures/colltest5/CollectionStrawManCC5_1.scala

@@ -423,7 +423,7 @@ object CollectionStrawMan5 {
     def start: Int
     def end: Int
     def apply(i: Int): A
-    def iterator: Iterator[A] = new Iterator[A] {
+    def iterator: Iterator[A]^{this} = new Iterator[A] {
       private var current = start
       def hasNext = current < end
       def next(): A = {