From c0051110633290af7c93109bf0cf12a042998f90 Mon Sep 17 00:00:00 2001
From: Devon Stewart <dstewart@twilio.com>
Date: Fri, 28 Dec 2018 12:46:46 -0800
Subject: [PATCH] Moving binary incompatible change out into
 FoldableSyntaxBinCompat0

---
 core/src/main/scala/cats/Foldable.scala       | 32 ----------------
 core/src/main/scala/cats/implicits.scala      |  1 +
 core/src/main/scala/cats/syntax/all.scala     |  3 ++
 .../src/main/scala/cats/syntax/foldable.scala | 38 +++++++++++++++++++
 4 files changed, 42 insertions(+), 32 deletions(-)

diff --git a/core/src/main/scala/cats/Foldable.scala b/core/src/main/scala/cats/Foldable.scala
index 211b5597779..f4256113027 100644
--- a/core/src/main/scala/cats/Foldable.scala
+++ b/core/src/main/scala/cats/Foldable.scala
@@ -506,38 +506,6 @@ import Foldable.sentinel
     )
   }
 
-  /**
-   * Separate this Foldable into a Tuple by an effectful separating function `A => G[Either[B, C]]`
-   * Equivalent to `Bitraversable#traverse` over `Alternative#separate`
-   *
-   * {{{
-   * scala> import cats.implicits._
-   * scala> val list = List(1,2,3,4)
-   * scala> val partitioned1 = Foldable[List].partitionEitherM(list)(a => if (a % 2 == 0) Eval.now(Either.left[String, Int](a.toString)) else Eval.now(Either.right[String, Int](a)))
-   * Since `Eval.now` yields a lazy computation, we need to force it to inspect the result:
-   * scala> partitioned1.value
-   * res0: (List[String], List[Int]) = (List(2, 4),List(1, 3))
-   * scala> val partitioned2 = Foldable[List].partitionEitherM(list)(a => Eval.later(Either.right(a * 4)))
-   * scala> partitioned2.value
-   * res1: (List[Nothing], List[Int]) = (List(),List(4, 8, 12, 16))
-   * }}}
-   */
-  def partitionEitherM[G[_], A, B, C](fa: F[A])(f: A => G[Either[B, C]])(implicit A: Alternative[F],
-                                                                         M: Monad[G]): G[(F[B], F[C])] = {
-    import cats.instances.tuple._
-
-    implicit val mb: Monoid[F[B]] = A.algebra[B]
-    implicit val mc: Monoid[F[C]] = A.algebra[C]
-
-    foldMapM[G, A, (F[B], F[C])](fa)(
-      a =>
-        M.map(f(a)) {
-          case Right(c) => (A.empty[B], A.pure(c))
-          case Left(b)  => (A.pure(b), A.empty[C])
-      }
-    )
-  }
-
   /**
    * Convert F[A] to a List[A], only including elements which match `p`.
    */
diff --git a/core/src/main/scala/cats/implicits.scala b/core/src/main/scala/cats/implicits.scala
index f04f033c732..1267851ae60 100644
--- a/core/src/main/scala/cats/implicits.scala
+++ b/core/src/main/scala/cats/implicits.scala
@@ -6,6 +6,7 @@ object implicits
     with syntax.AllSyntaxBinCompat1
     with syntax.AllSyntaxBinCompat2
     with syntax.AllSyntaxBinCompat3
+    with syntax.AllSyntaxBinCompat4
     with instances.AllInstances
     with instances.AllInstancesBinCompat0
     with instances.AllInstancesBinCompat1
diff --git a/core/src/main/scala/cats/syntax/all.scala b/core/src/main/scala/cats/syntax/all.scala
index ec7fbec6308..106efac663b 100644
--- a/core/src/main/scala/cats/syntax/all.scala
+++ b/core/src/main/scala/cats/syntax/all.scala
@@ -7,6 +7,7 @@ abstract class AllSyntaxBinCompat
     with AllSyntaxBinCompat1
     with AllSyntaxBinCompat2
     with AllSyntaxBinCompat3
+    with AllSyntaxBinCompat4
 
 trait AllSyntax
     extends AlternativeSyntax
@@ -77,3 +78,5 @@ trait AllSyntaxBinCompat2
     with ValidatedSyntaxBincompat0
 
 trait AllSyntaxBinCompat3 extends UnorderedFoldableSyntax with Function1Syntax
+
+trait AllSyntaxBinCompat4 extends FoldableSyntaxBinCompat0
diff --git a/core/src/main/scala/cats/syntax/foldable.scala b/core/src/main/scala/cats/syntax/foldable.scala
index 2df84238472..5e5f713b916 100644
--- a/core/src/main/scala/cats/syntax/foldable.scala
+++ b/core/src/main/scala/cats/syntax/foldable.scala
@@ -190,5 +190,43 @@ final class FoldableOps[F[_], A](private val fa: F[A]) extends AnyVal {
           case None ⇒ acc
       }
     )
+}
+
+trait FoldableSyntaxBinCompat0 {
+  implicit final def catsSyntaxFoldableBinCompat0[F[_]](fa: Foldable[F]): FoldableOpsBinCompat0[F] =
+    new FoldableOpsBinCompat0(fa)
+}
+
+final class FoldableOpsBinCompat0[F[_]](private val F: Foldable[F]) extends AnyVal {
+  /**
+   * Separate this Foldable into a Tuple by an effectful separating function `A => G[Either[B, C]]`
+   * Equivalent to `Bitraversable#traverse` over `Alternative#separate`
+   *
+   * {{{
+   * scala> import cats.implicits._, cats.Foldable, cats.Eval
+   * scala> val list = List(1,2,3,4)
+   * scala> val partitioned1 = Foldable[List].partitionEitherM(list)(a => if (a % 2 == 0) Eval.now(Either.left[String, Int](a.toString)) else Eval.now(Either.right[String, Int](a)))
+   * Since `Eval.now` yields a lazy computation, we need to force it to inspect the result:
+   * scala> partitioned1.value
+   * res0: (List[String], List[Int]) = (List(2, 4),List(1, 3))
+   * scala> val partitioned2 = Foldable[List].partitionEitherM(list)(a => Eval.later(Either.right(a * 4)))
+   * scala> partitioned2.value
+   * res1: (List[Nothing], List[Int]) = (List(),List(4, 8, 12, 16))
+   * }}}
+   */
+  def partitionEitherM[G[_], A, B, C](fa: F[A])(f: A => G[Either[B, C]])(implicit A: Alternative[F],
+                                                                         M: Monad[G]): G[(F[B], F[C])] = {
+    import cats.instances.tuple._
+
+    implicit val mb: Monoid[F[B]] = A.algebra[B]
+    implicit val mc: Monoid[F[C]] = A.algebra[C]
 
+    F.foldMapM[G, A, (F[B], F[C])](fa)(
+      a =>
+        M.map(f(a)) {
+          case Right(c) => (A.empty[B], A.pure(c))
+          case Left(b)  => (A.pure(b), A.empty[C])
+      }
+    )
+  }
 }