Add Future instances to implicit scope

core/src/main/scala/cats/Invariant.scala

@@ -4,10 +4,11 @@ import cats.arrow.Arrow
 import cats.kernel._
 import simulacrum.typeclass
 import cats.kernel.compat.scalaVersionSpecific._
+import scala.annotation.implicitNotFound
 import scala.collection.immutable.{Queue, SortedMap}
+import scala.concurrent.{ExecutionContext, Future}
 import scala.util.Try
 import scala.util.control.TailCalls.TailRec
-import scala.annotation.implicitNotFound
 
 /**
  * Must obey the laws defined in cats.laws.InvariantLaws.
@@ -129,6 +130,10 @@ object Invariant extends ScalaVersionSpecificInvariantInstances with InvariantIn
 
  implicit def catsInstancesForTry: MonadError[Try, Throwable] with CoflatMap[Try] =
  cats.instances.try_.catsStdInstancesForTry
+ implicit def catsInstancesForFuture(implicit
+ ec: ExecutionContext
+ ): MonadError[Future, Throwable] with CoflatMap[Future] =
+ cats.instances.future.catsStdInstancesForFuture(ec)
 
  implicit def catsContravariantMonoidalForOrder: ContravariantMonoidal[Order] =
  cats.instances.order.catsContravariantMonoidalForOrder

core/src/main/scala/cats/Semigroupal.scala

@@ -2,6 +2,7 @@ package cats
 
 import cats.kernel.CommutativeSemigroup
 import scala.collection.immutable.{Queue, SortedMap, SortedSet}
+import scala.concurrent.{ExecutionContext, Future}
 import scala.util.Try
 import simulacrum.typeclass
 import scala.annotation.implicitNotFound
@@ -50,6 +51,8 @@ import scala.annotation.implicitNotFound
 object Semigroupal extends ScalaVersionSpecificSemigroupalInstances with SemigroupalArityFunctions {
  implicit def catsSemigroupalForOption: Semigroupal[Option] = cats.instances.option.catsStdInstancesForOption
  implicit def catsSemigroupalForTry: Semigroupal[Try] = cats.instances.try_.catsStdInstancesForTry
+ implicit def catsSemigroupalForFuture(implicit ec: ExecutionContext): Semigroupal[Future] =
+ cats.instances.future.catsStdInstancesForFuture(ec)
  implicit def catsSemigroupalForList: Semigroupal[List] = cats.instances.list.catsStdInstancesForList
  implicit def catsSemigroupalForVector: Semigroupal[Vector] = cats.instances.vector.catsStdInstancesForVector
  implicit def catsSemigroupalForQueue: Semigroupal[Queue] = cats.instances.queue.catsStdInstancesForQueue

js/src/test/scala/cats/tests/FutureTests.scala

@@ -1,7 +1,6 @@
 package cats.js.tests
 
 import cats.Comonad
-import cats.instances.FutureInstances
 import cats.js.instances.Await
 import cats.js.instances.future.futureComonad
 import cats.kernel.Eq
@@ -15,7 +14,7 @@ import org.scalacheck.Arbitrary.arbitrary
 import scala.concurrent.{ExecutionContextExecutor, Future}
 import scala.concurrent.duration._
 
-class FutureTests extends CatsSuite with FutureInstances {
+class FutureTests extends CatsSuite {
  // Replaces Scala.js's `JSExecutionContext.runNow`, which is removed in 1.0.
  // TODO: We shouldn't do this! See: https://github.com/scala-js/scala-js/issues/2102
  implicit private object RunNowExecutionContext extends ExecutionContextExecutor {

jvm/src/test/scala/cats/tests/FutureSuite.scala

@@ -1,6 +1,5 @@
 package cats.jvm.tests
 
-import cats.instances.future._
 import cats.kernel.{Eq, Semigroup}
 import cats.kernel.laws.discipline.{MonoidTests => MonoidLawTests, SemigroupTests => SemigroupLawTests}
 import cats.laws.discipline._

kernel/src/main/scala/cats/kernel/Semigroup.scala

@@ -2,6 +2,7 @@ package cats.kernel
 
 import scala.annotation.tailrec
 import scala.collection.immutable.{BitSet, Queue, SortedMap, SortedSet}
+import scala.concurrent.{ExecutionContext, Future}
 import scala.concurrent.duration.{Duration, FiniteDuration}
 import scala.{specialized => sp}
 import scala.util.{Failure, Success, Try}
@@ -250,6 +251,8 @@ private[kernel] trait MonoidInstances extends BandInstances {
  cats.kernel.instances.either.catsDataMonoidForEither[A, B]
  implicit def catsKernelMonoidForTry[A: Monoid]: Monoid[Try[A]] =
  new TryMonoid[A](Monoid[A])
+ implicit def catsKernelMonoidForFuture[A](implicit A: Monoid[A], ec: ExecutionContext): Monoid[Future[A]] =
+ new FutureMonoid[A](A, ec)
  implicit def catsKernelMonoidForOption[A: Semigroup]: Monoid[Option[A]] =
  cats.kernel.instances.option.catsKernelStdMonoidForOption[A]
 }
@@ -277,6 +280,8 @@ private[kernel] trait SemigroupInstances {
  cats.kernel.instances.either.catsDataSemigroupForEither[A, B]
  implicit def catsKernelSemigroupForTry[A: Semigroup]: Semigroup[Try[A]] =
  new TrySemigroup[A](Semigroup[A])
+ implicit def catsKernelSemigroupForFuture[A](implicit A: Semigroup[A], ec: ExecutionContext): Semigroup[Future[A]] =
+ new FutureSemigroup[A](A, ec)
 }
 
 private class TryMonoid[A](A: Monoid[A]) extends TrySemigroup[A](A) with Monoid[Try[A]] {
@@ -291,3 +296,13 @@ private class TrySemigroup[A](A: Semigroup[A]) extends Semigroup[Try[A]] {
  case (_, f) => f
  }
 }
+
+private class FutureMonoid[A](A: Monoid[A], ec: ExecutionContext)
+ extends FutureSemigroup[A](A, ec)
+ with Monoid[Future[A]] {
+ def empty: Future[A] = Future.successful(A.empty)
+}
+
+private class FutureSemigroup[A](A: Semigroup[A], ec: ExecutionContext) extends Semigroup[Future[A]] {
+ def combine(x: Future[A], y: Future[A]): Future[A] = x.flatMap(xv => y.map(A.combine(xv, _))(ec))(ec)
+}