Capturecheck all files in generic

Author: odersky

tests/pos-special/stdlib/collection/generic/BitOperations.scala

@@ -0,0 +1,51 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala.collection
+package generic
+import language.experimental.captureChecking
+
+
+/** Some bit operations.
+  *
+  *  See [[https://www.drmaciver.com/2008/08/unsigned-comparison-in-javascala/]] for
+  *  an explanation of unsignedCompare.
+  */
+private[collection] object BitOperations {
+  trait Int {
+    type Int = scala.Int
+    def zero(i: Int, mask: Int)                 = (i & mask) == 0
+    def mask(i: Int, mask: Int)                 = i & (complement(mask - 1) ^ mask)
+    def hasMatch(key: Int, prefix: Int, m: Int) = mask(key, m) == prefix
+    def unsignedCompare(i: Int, j: Int)         = (i < j) ^ (i < 0) ^ (j < 0)
+    def shorter(m1: Int, m2: Int)               = unsignedCompare(m2, m1)
+    def complement(i: Int)                      = (-1) ^ i
+    def bits(num: Int)                          = 31 to 0 by -1 map (i => (num >>> i & 1) != 0)
+    def bitString(num: Int, sep: String = "")   = bits(num) map (b => if (b) "1" else "0") mkString sep
+    def highestOneBit(j: Int)                   = java.lang.Integer.highestOneBit(j)
+  }
+  object Int extends Int
+
+  trait Long {
+    type Long = scala.Long
+    def zero(i: Long, mask: Long)                  = (i & mask) == 0L
+    def mask(i: Long, mask: Long)                  = i & (complement(mask - 1) ^ mask)
+    def hasMatch(key: Long, prefix: Long, m: Long) = mask(key, m) == prefix
+    def unsignedCompare(i: Long, j: Long)          = (i < j) ^ (i < 0L) ^ (j < 0L)
+    def shorter(m1: Long, m2: Long)                = unsignedCompare(m2, m1)
+    def complement(i: Long)                        = (-1L) ^ i
+    def bits(num: Long)                            = 63L to 0L by -1L map (i => (num >>> i & 1L) != 0L)
+    def bitString(num: Long, sep: String = "")     = bits(num) map (b => if (b) "1" else "0") mkString sep
+    def highestOneBit(j: Long)                     = java.lang.Long.highestOneBit(j)
+  }
+  object Long extends Long
+}

tests/pos-special/stdlib/collection/generic/DefaultSerializationProxy.scala

@@ -0,0 +1,90 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala.collection.generic
+
+import java.io.{ObjectInputStream, ObjectOutputStream}
+
+import scala.collection.{Factory, Iterable}
+import scala.collection.mutable.Builder
+import language.experimental.captureChecking
+import scala.annotation.unchecked.uncheckedCaptures
+
+/** The default serialization proxy for collection implementations.
+  *
+  * This class is `final` and requires an extra `Factory` object rather than leaving the details of creating a `Builder`
+  * to an abstract method that could be implemented by a subclass. This is necessary because the factory is needed
+  * for deserializing this class's private state, which happens before any subclass fields would be deserialized. Any
+  * additional state required to create the proper `Builder` needs to be captured by the `factory`.
+  */
+@SerialVersionUID(3L)
+final class DefaultSerializationProxy[A](factory: Factory[A, Any], @transient private[this] val coll: Iterable[A]) extends Serializable {
+
+  @transient protected var builder: Builder[A @uncheckedCaptures, Any] = _
+    // @uncheckedCaptures OK since builder is used only locally when reading objects
+
+  private[this] def writeObject(out: ObjectOutputStream): Unit = {
+    out.defaultWriteObject()
+    val k = coll.knownSize
+    out.writeInt(k)
+    var count = 0
+    coll.foreach { x =>
+      out.writeObject(x)
+      count += 1
+    }
+    if(k >= 0) {
+      if(count != k) throw new IllegalStateException(s"Illegal size $count of collection, expected $k")
+    } else out.writeObject(SerializeEnd)
+  }
+
+  private[this] def readObject(in: ObjectInputStream): Unit = {
+    in.defaultReadObject()
+    builder = factory.newBuilder
+    val k = in.readInt()
+    if(k >= 0) {
+      builder.sizeHint(k)
+      var count = 0
+      while(count < k) {
+        builder += in.readObject().asInstanceOf[A]
+        count += 1
+      }
+    } else {
+      while (true) in.readObject match {
+        case SerializeEnd => return
+        case a => builder += a.asInstanceOf[A]
+      }
+    }
+  }
+
+  protected[this] def readResolve(): Any = builder.result()
+}
+
+@SerialVersionUID(3L)
+private[collection] case object SerializeEnd
+
+/** Mix-in trait to enable DefaultSerializationProxy for the standard collection types. Depending on the type
+  * it is mixed into, it will dynamically choose `iterableFactory`, `mapFactory`, `sortedIterableFactory` or
+  * `sortedMapFactory` for deserialization into the respective `CC` type. Override `writeReplace` or implement
+  * it directly without using this trait if you need a non-standard factory or if you want to use a different
+  * serialization scheme.
+  */
+trait DefaultSerializable extends Serializable { this: scala.collection.Iterable[_] =>
+  protected[this] def writeReplace(): AnyRef = {
+    val f: Factory[Any, Any] = this match {
+      case it: scala.collection.SortedMap[_, _] => it.sortedMapFactory.sortedMapFactory[Any, Any](it.ordering.asInstanceOf[Ordering[Any]]).asInstanceOf[Factory[Any, Any]]
+      case it: scala.collection.Map[_, _] => it.mapFactory.mapFactory[Any, Any].asInstanceOf[Factory[Any, Any]]
+      case it: scala.collection.SortedSet[_] => it.sortedIterableFactory.evidenceIterableFactory[Any](it.ordering.asInstanceOf[Ordering[Any]])
+      case it => it.iterableFactory.iterableFactory
+    }
+    new DefaultSerializationProxy(f, this)
+  }
+}

tests/pos-special/stdlib/collection/generic/IsIterable.scala

@@ -0,0 +1,165 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala.collection
+package generic
+import language.experimental.captureChecking
+
+/** A trait which can be used to avoid code duplication when defining extension
+ *  methods that should be applicable both to existing Scala collections (i.e.,
+ *  types extending `Iterable`) as well as other (potentially user-defined)
+ *  types that could be converted to a Scala collection type. This trait
+ *  makes it possible to treat Scala collections and types that can be implicitly
+ *  converted to a collection type uniformly. For example, one can provide
+ *  extension methods that work both on collection types and on `String`s (`String`s
+ *  do not extend `Iterable`, but can be converted to `Iterable`)
+ *
+ * `IsIterable` provides three members:
+ *
+ *  1. type member `A`, which represents the element type of the target `Iterable[A]`
+ *  1. type member `C`, which represents the type returned by transformation operations that preserve the collection’s elements type
+ *  1. method `apply`, which provides a way to convert between the type we wish to add extension methods to, `Repr`, and `IterableOps[A, Iterable, C]`.
+ *
+ * ===Usage===
+ *
+ * One must provide `IsIterable` as an implicit parameter type of an implicit
+ * conversion. Its usage is shown below. Our objective in the following example
+ * is to provide a generic extension method `mapReduce` to any type that extends
+ * or can be converted to `Iterable`. In our example, this includes
+ * `String`.
+ *
+ * {{{
+ *    import scala.collection.{Iterable, IterableOps}
+ *    import scala.collection.generic.IsIterable
+ *
+ *    class ExtensionMethods[Repr, I <: IsIterable[Repr]](coll: Repr, it: I) {
+ *      def mapReduce[B](mapper: it.A => B)(reducer: (B, B) => B): B = {
+ *        val iter = it(coll).iterator
+ *        var res = mapper(iter.next())
+ *        while (iter.hasNext)
+ *          res = reducer(res, mapper(iter.next()))
+ *        res
+ *      }
+ *    }
+ *
+ *    implicit def withExtensions[Repr](coll: Repr)(implicit it: IsIterable[Repr]): ExtensionMethods[Repr, it.type] =
+ *      new ExtensionMethods(coll, it)
+ *
+ *  // See it in action!
+ *  List(1, 2, 3).mapReduce(_ * 2)(_ + _) // res0: Int = 12
+ *  "Yeah, well, you know, that's just, like, your opinion, man.".mapReduce(x => 1)(_ + _) // res1: Int = 59
+ *}}}
+ *
+ * Here, we begin by creating a class `ExtensionMethods` which contains our
+ * `mapReduce` extension method.
+ *
+ * Note that `ExtensionMethods` takes a constructor argument `coll` of type `Repr`, where
+ * `Repr` represents (typically) the collection type, and an argument `it` of a subtype of `IsIterable[Repr]`.
+ * The body of the method starts by converting the `coll` argument to an `IterableOps` in order to
+ * call the `iterator` method on it.
+ * The remaining of the implementation is straightforward.
+ *
+ * The `withExtensions` implicit conversion makes the `mapReduce` operation available
+ * on any type `Repr` for which it exists an implicit `IsIterable[Repr]` instance.
+ * Note how we keep track of the precise type of the implicit `it` argument by using the
+ * `it.type` singleton type, rather than the wider `IsIterable[Repr]` type. We do that
+ * so that the information carried by the type members `A` and `C` of the `it` argument
+ * is not lost.
+ *
+ * When the `mapReduce` method is called on some type of which it is not
+ * a member, implicit search is triggered. Because implicit conversion
+ * `withExtensions` is generic, it will be applied as long as an implicit
+ * value of type `IsIterable[Repr]` can be found. Given that the
+ * `IsIterable` companion object contains implicit members that return values of type
+ * `IsIterable`, this requirement is typically satisfied, and the chain
+ * of interactions described in the previous paragraph is set into action.
+ * (See the `IsIterable` companion object, which contains a precise
+ * specification of the available implicits.)
+ *
+ * ''Note'': Currently, it's not possible to combine the implicit conversion and
+ * the class with the extension methods into an implicit class due to
+ * limitations of type inference.
+ *
+ * ===Implementing `IsIterable` for New Types===
+ *
+ * One must simply provide an implicit value of type `IsIterable`
+ * specific to the new type, or an implicit conversion which returns an
+ * instance of `IsIterable` specific to the new type.
+ *
+ * Below is an example of an implementation of the `IsIterable` trait
+ * where the `Repr` type is `Range`.
+ *
+ *{{{
+ * implicit val rangeRepr: IsIterable[Range] { type A = Int; type C = IndexedSeq[Int] } =
+ *   new IsIterable[Range] {
+ *     type A = Int
+ *     type C = IndexedSeq[Int]
+ *     def apply(coll: Range): IterableOps[Int, IndexedSeq, IndexedSeq[Int]] = coll
+ *   }
+ *}}}
+ *
+ * (Note that in practice the `IsIterable[Range]` instance is already provided by
+ * the standard library, and it is defined as an `IsSeq[Range]` instance)
+ */
+trait IsIterable[Repr] extends IsIterableOnce[Repr] {
+
+  /** The type returned by transformation operations that preserve the same elements
+    * type (e.g. `filter`, `take`).
+    *
+    * In practice, this type is often `Repr` itself, excepted in the case
+    * of `SeqView[A]` (and other `View[A]` subclasses), where it is “only” `View[A]`.
+    */
+  type C
+
+  @deprecated("'conversion' is now a method named 'apply'", "2.13.0")
+  override val conversion: Repr => IterableOps[A, Iterable, C] = apply(_)
+
+  /** A conversion from the type `Repr` to `IterableOps[A, Iterable, C]` */
+  def apply(coll: Repr): IterableOps[A, Iterable, C]
+
+}
+
+object IsIterable extends IsIterableLowPriority {
+
+  // Straightforward case: IterableOps subclasses
+  implicit def iterableOpsIsIterable[A0, CC0[X] <: IterableOps[X, Iterable, CC0[X]]]: IsIterable[CC0[A0]] { type A = A0; type C = CC0[A0] } =
+    new IsIterable[CC0[A0]] {
+      type A = A0
+      type C = CC0[A0]
+      def apply(coll: CC0[A]): IterableOps[A, Iterable, C] = coll
+    }
+
+  // The `BitSet` type can not be unified with the `CC0` parameter of
+  // the above definition because it does not take a type parameter.
+  // Hence the need for a separate case:
+  implicit def bitSetOpsIsIterable[C0 <: BitSet with BitSetOps[C0]]: IsIterable[C0] { type A = Int; type C = C0 } =
+    new IsIterable[C0] {
+      type A = Int
+      type C = C0
+      def apply(coll: C0): IterableOps[Int, Iterable, C0] = coll
+    }
+
+}
+
+trait IsIterableLowPriority {
+
+  // Makes `IsSeq` instances visible in `IsIterable` companion
+  implicit def isSeqLikeIsIterable[Repr](implicit
+    isSeqLike: IsSeq[Repr]
+  ): IsIterable[Repr] { type A = isSeqLike.A; type C = isSeqLike.C } = isSeqLike
+
+  // Makes `IsMap` instances visible in `IsIterable` companion
+  implicit def isMapLikeIsIterable[Repr](implicit
+    isMapLike: IsMap[Repr]
+  ): IsIterable[Repr] { type A = isMapLike.A; type C = isMapLike.C } = isMapLike
+
+}

tests/pos-special/stdlib/collection/generic/IsIterableOnce.scala

@@ -0,0 +1,72 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala
+package collection
+package generic
+import language.experimental.captureChecking
+
+/** Type class witnessing that a collection representation type `Repr` has
+ *  elements of type `A` and has a conversion to `IterableOnce[A]`.
+ *
+ *  This type enables simple enrichment of `IterableOnce`s with extension
+ *  methods which can make full use of the mechanics of the Scala collections
+ *  framework in their implementation.
+ *
+ *  Example usage,
+ * {{{
+ *    class FilterMapImpl[Repr, I <: IsIterableOnce[Repr]](coll: Repr, it: I) {
+ *      final def filterMap[B, That](f: it.A => Option[B])(implicit bf: BuildFrom[Repr, B, That]): That = {
+ *        val b = bf.newBuilder(coll)
+ *        for(e <- it(coll).iterator) f(e) foreach (b +=)
+ *        b.result()
+ *      }
+ *    }
+ *    implicit def filterMap[Repr](coll: Repr)(implicit it: IsIterableOnce[Repr]): FilterMapImpl[Repr, it.type] =
+ *      new FilterMapImpl(coll, it)
+ *
+ *    List(1, 2, 3, 4, 5) filterMap (i => if(i % 2 == 0) Some(i) else None)
+ *    // == List(2, 4)
+ * }}}
+ */
+trait IsIterableOnce[Repr] {
+
+  /** The type of elements we can traverse over (e.g. `Int`). */
+  type A
+
+  @deprecated("'conversion' is now a method named 'apply'", "2.13.0")
+  val conversion: Repr => IterableOnce[A] = apply(_)
+
+  /** A conversion from the representation type `Repr` to a `IterableOnce[A]`. */
+  def apply(coll: Repr): IterableOnce[A]
+
+}
+
+object IsIterableOnce extends IsIterableOnceLowPriority {
+
+  // Straightforward case: IterableOnce subclasses
+  implicit def iterableOnceIsIterableOnce[CC0[A] <: IterableOnce[A], A0]: IsIterableOnce[CC0[A0]] { type A = A0 } =
+    new IsIterableOnce[CC0[A0]] {
+      type A = A0
+      def apply(coll: CC0[A0]): IterableOnce[A0] = coll
+    }
+
+}
+
+trait IsIterableOnceLowPriority {
+
+  // Makes `IsIterable` instance visible in `IsIterableOnce` companion
+  implicit def isIterableLikeIsIterableOnce[Repr](implicit
+    isIterableLike: IsIterable[Repr]
+  ): IsIterableOnce[Repr] { type A = isIterableLike.A } = isIterableLike
+
+}