Add an implementation of IsSeq for IArray.

instead of just casting the Array variant, the underlying collection
type should be immutable.ArraySeq.

Author: bishabosha

library/src/scala/collection/generic/IsSeq.scala

@@ -18,6 +18,7 @@ import language.experimental.captureChecking
 import caps.unsafe.untrackedCaptures
 
 import scala.reflect.ClassTag
+import scala.annotation.experimental
 
 /** Type class witnessing that a collection representation type `Repr` has
   * elements of type `A` and has a conversion to `SeqOps[A, Iterable, C]`, for
@@ -106,6 +107,25 @@ object IsSeq {
         }
     }
 
+  @experimental
+  given iarrayIsSeq[A0 : ClassTag]: (IsSeq[IArray[A0]] { type A = A0; type C = IArray[A0] }) =
+    new IsSeq[IArray[A0]] {
+      type A = A0
+      type C = IArray[A0]
+      def apply(a: IArray[A0]): SeqOps[A0, Seq, IArray[A0]] =
+        new SeqOps[A, immutable.ArraySeq, IArray[A]] {
+          def apply(i: Int): A = a(i)
+          def length: Int = a.length
+          def toIterable: Iterable[A] = IArray.genericWrapArray(a)
+          protected def coll: IArray[A] = a
+          protected def fromSpecific(coll: IterableOnce[A]^): IArray[A] = IArray.from(coll)
+          def iterableFactory: IterableFactory[immutable.ArraySeq] = immutable.ArraySeq.untagged
+          override def empty: IArray[A] = IArray.empty[A]
+          protected def newSpecificBuilder: mutable.Builder[A, IArray[A]] = IArray.newBuilder
+          def iterator: Iterator[A] = a.iterator
+        }
+    }
+
   // `Range` can not be unified with the `CC0` parameter of the
   // `seqOpsIsSeq` definition because it does not take a type parameter.
   // Hence the need for a separate case:

project/MiMaFilters.scala

@@ -23,6 +23,9 @@ object MiMaFilters {
         ProblemFilters.exclude[DirectMissingMethodProblem]("scala.NamedTuple.namedTupleOrdering"),
         ProblemFilters.exclude[MissingClassProblem]("scala.NamedTuple$namedTupleOrdering"),
 
+        // IArray integration with Scala Collections:
+        ProblemFilters.exclude[DirectMissingMethodProblem]("scala.collection.generic.IsSeq.iarrayIsSeq"),
+
 		// cc related
         ProblemFilters.exclude[MissingClassProblem]("scala.annotation.internal.readOnlyCapability"),
         ProblemFilters.exclude[MissingClassProblem]("scala.annotation.internal.onlyCapability"),

tests/run-tasty-inspector/stdlibExperimentalDefinitions.scala

@@ -98,6 +98,9 @@ val experimentalDefinitionInLibrary = Set(
 
   // New feature: Erased trait
   "scala.compiletime.Erased",
+
+  // New API: IsSeq[IArray[T]]
+  "scala.collection.generic.IsSeq$.iarrayIsSeq",
 )
 
 

tests/run/IArrayOps-experimental.check

@@ -0,0 +1,2 @@
+class scala.collection.immutable.ArraySeq$ofRef
+1,2

tests/run/IArrayOps-experimental.scala

@@ -0,0 +1,16 @@
+//> using options -experimental
+
+@main def Test: Unit =
+  val isSeq1: scala.collection.generic.IsSeq[IArray[Int]] { type A = Int; type C = IArray[Int] } =
+    scala.collection.generic.IsSeq.iarrayIsSeq[Int]
+  val isSeq2: scala.collection.generic.IsSeq[IArray[Int]] { type A = Int; type C = IArray[Int] } =
+    summon[scala.collection.generic.IsSeq[IArray[Int]]]
+  assert(isSeq1.getClass eq isSeq2.getClass) // check that default implicit is same as explicit call
+
+  val iarr = IArray(1, 2, 3)
+  val seqOps: scala.collection.SeqOps[Int, Iterable, IArray[Int]] = isSeq1(iarr)
+  println(seqOps.map(_ * 2).getClass()) // should be immutable.ArraySeq.ofRef
+  val evens: IArray[Int] = seqOps.filter(_ % 2 == 0)
+  val buckets: Map[Boolean, IArray[Int]] = seqOps.groupBy(_ < 3)
+  val smalls: IArray[Int] = buckets(true)
+  println(smalls.mkString(","))