Hash typeclass

build.sbt

@@ -236,7 +236,123 @@ val binaryCompatibleVersion = "0.8.0"
 val binaryCompatibleExceptions = {
   import com.typesafe.tools.mima.core._
   import com.typesafe.tools.mima.core.ProblemFilters._
-  Seq( //todo: remove these once we release 1.0.0-RC1
+  Seq( // todo: remove these once we release 1.0.0-RC1
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.QueueInstances.*"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.QueueInstances1.*"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.QueueInstances2.*"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.DurationInstances.*"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.MapInstances.catsKernelStdEqForMap"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.MapInstances.catsKernelStdMonoidForMap"),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.MapInstances.catsKernelStdHashForMap"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple12"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple7"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple4"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple13"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple11"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple1"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple7"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple16"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple22"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple1"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple14"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple4"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple20"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple19"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple10"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple17"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple18"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple3"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple9"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple6"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple3"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple12"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple22"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple6"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple19"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple10"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple9"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple21"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple15"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple13"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple16"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple20"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple14"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple5"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple2"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple8"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple17"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple5"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple15"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple21"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple11"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdPartialOrderForTuple2"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple8"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.TupleInstances.catsKernelStdEqForTuple18"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple9"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple16"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple22"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple3"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple6"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple21"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple18"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple12"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple15"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple8"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple2"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple5"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple20"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple14"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple17"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple4"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple11"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple7"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple1"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple10"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple19"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple13"),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.StreamInstances1.catsKernelStdHashForStream"),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.ListInstances1.catsKernelStdHashForList"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.SetInstances.catsKernelStdPartialOrderForSet"),
+    exclude[UpdateForwarderBodyProblem]("cats.kernel.instances.SetInstances.catsKernelStdSemilatticeForSet"),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.SetInstances.catsKernelStdHashForSet"),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.VectorInstances1.catsKernelStdHashForVector"),
+    exclude[DirectMissingMethodProblem]("cats.kernel.instances.BitSetInstances.catsKernelStdPartialOrderForBitSet"),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.BitSetInstances.cats$kernel$instances$BitSetInstances$_setter_$catsKernelStdOrderForBitSet_="),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.BitSetInstances.catsKernelStdOrderForBitSet"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple9"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple16"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple22"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple3"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple6"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple21"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple18"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple12"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple15"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple8"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple2"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple5"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple20"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple14"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple17"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple4"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple11"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple7"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple1"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple10"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple19"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.TupleInstances1.catsKernelStdHashForTuple13"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.EitherInstances1.catsStdEqForEither"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.EitherInstances.catsStdOrderForEither"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.EitherInstances.catsDataMonoidForEither"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.EitherInstances0.catsDataSemigroupForEither"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.EitherInstances0.catsStdHashForEither"),
+    exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.EitherInstances0.catsStdPartialOrderForEither"),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.OptionInstances1.catsKernelStdHashForOption"),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.FunctionInstances0.catsKernelHashForFunction0"),
+    exclude[ReversedMissingMethodProblem]("cats.kernel.instances.EitherInstances0.catsStdHashForEither"),
+    exclude[DirectMissingMethodProblem]("cats.kernel.instances.all.package.catsKernelStdPartialOrderForBitSet"),
+    exclude[DirectMissingMethodProblem]("cats.kernel.instances.bitSet.package.catsKernelStdPartialOrderForBitSet"),
+    //todo: remove these once we release 1.0.0-RC1
     exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.QueueInstances.*"),
     exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.QueueInstances1.*"),
     exclude[InheritedNewAbstractMethodProblem]("cats.kernel.instances.QueueInstances2.*"),

core/src/main/scala/cats/instances/all.scala

@@ -11,6 +11,7 @@ trait AllInstances
   with    EquivInstances
   with    FunctionInstances
   with    FutureInstances
+  with    HashInstances
   with    ListInstances
   with    MapInstances
   with    MonoidInstances

core/src/main/scala/cats/instances/hash.scala

@@ -0,0 +1,16 @@
+package cats
+package instances
+
+
+trait HashInstances {
+
+  implicit val catsContravariantForHash: Contravariant[Hash] =
+    new Contravariant[Hash] {
+      /**
+       * Derive a `Hash` for `B` given an `Hash[A]` and a function `B => A`.
+       */
+      def contramap[A, B](ha: Hash[A])(f: B => A): Hash[B] = Hash.by(f)(ha)
+
+    }
+
+}

core/src/main/scala/cats/package.scala

@@ -78,13 +78,15 @@ package object cats {
   type Eq[A] = cats.kernel.Eq[A]
   type PartialOrder[A] = cats.kernel.PartialOrder[A]
   type Order[A] = cats.kernel.Order[A]
+  type Hash[A] = cats.kernel.Hash[A]
   type Semigroup[A] = cats.kernel.Semigroup[A]
   type Monoid[A] = cats.kernel.Monoid[A]
   type Group[A] = cats.kernel.Group[A]
 
   val Eq = cats.kernel.Eq
   val PartialOrder = cats.kernel.PartialOrder
   val Order = cats.kernel.Order
+  val Hash = cats.kernel.Hash
   val Semigroup = cats.kernel.Semigroup
   val Monoid = cats.kernel.Monoid
   val Group = cats.kernel.Group

core/src/main/scala/cats/syntax/all.scala

@@ -22,6 +22,7 @@ trait AllSyntax
     with FoldableSyntax
     with FunctorSyntax
     with GroupSyntax
+    with HashSyntax
     with InvariantSyntax
     with IorSyntax
     with ListSyntax

core/src/main/scala/cats/syntax/hash.scala

@@ -0,0 +1,18 @@
+package cats
+package syntax
+
+import cats.macros.Ops
+
+trait HashSyntax {
+
+  implicit def catsSyntaxHash[A: Hash](a: A): HashOps[A] =
+    new HashOps[A](a)
+
+}
+
+final class HashOps[A: Hash](a: A) {
+  /**
+   * Gets the hash code of this object given an implicit `Hash` instance.
+   */
+  def hash: Int = macro Ops.unop0[Int]
+}

kernel-laws/src/main/scala/cats/kernel/laws/HashLaws.scala

@@ -0,0 +1,58 @@
+package cats.kernel
+package laws
+
+import org.typelevel.discipline._
+import org.scalacheck._
+import org.scalacheck.Prop._
+
+import scala.util.hashing._
+
+object HashLaws {
+  def apply[A : Eq : Arbitrary]: HashLaws[A] =
+    new HashLaws[A] {
+      def Equ = implicitly[Eq[A]]
+      def Arb = implicitly[Arbitrary[A]]
+    }
+}
+
+/**
+ * @author Tongfei Chen
+ */
+trait HashLaws[A] extends Laws {
+
+  implicit def Equ: Eq[A]
+  implicit def Arb: Arbitrary[A]
+
+  def hash(implicit A: Hash[A]): HashProperties = new HashProperties(
+    name = "hash",
+    parent = None,
+    Rules.serializable(Equ),
+    "compatibility-hash" -> forAll { (x: A, y: A) =>
+      !(A.eqv(x, y)) ?|| (Hash.hash(x) == Hash.hash(y))
+    }
+  )
+
+  def sameAsUniversalHash(implicit A: Hash[A]): HashProperties = new HashProperties(
+    name = "sameAsUniversalHash",
+    parent = None,
+    Rules.serializable(Equ),
+    "same-as-universal-hash" -> forAll { (x: A, y: A) =>
+      (A.hash(x) == x.hashCode) && (Hash.fromUniversalHashCode[A].hash(x) == x.hashCode()) &&
+        (A.eqv(x, y) == Hash.fromUniversalHashCode[A].eqv(x, y))
+    }
+  )
+
+  def sameAsScalaHashing(implicit catsHash: Hash[A], scalaHashing: Hashing[A]): HashProperties = new HashProperties(
+    name = "sameAsScalaHashing",
+    parent = None,
+    Rules.serializable(Equ),
+    "same-as-scala-hashing" -> forAll { (x: A, y: A) =>
+      (catsHash.hash(x) == Hash.fromHashing(scalaHashing).hash(x)) &&
+        (catsHash.eqv(x, y) == Hash.fromHashing(scalaHashing).eqv(x, y))
+    }
+  )
+
+  class HashProperties(name: String, parent: Option[RuleSet], props: (String, Prop)*)
+  extends DefaultRuleSet(name, parent, props: _*)
+
+}