alleycats - Extract[F[_]] the only way to get the syntax is the deprecated one

alleycats-core/src/main/scala/alleycats/syntax/all.scala

@@ -21,4 +21,4 @@
 
 package alleycats.syntax
 
-object all extends EmptySyntax with FoldableSyntax
+object all extends EmptySyntax with FoldableSyntax with ExtractSyntax

alleycats-core/src/main/scala/alleycats/syntax/extract.scala

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2015 Typelevel
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package alleycats
+package syntax
+
+import alleycats.Extract
+
+object extract extends ExtractSyntax
+
+trait ExtractSyntax {
+  implicit final def catsSyntaxExtract[F[_], A](fa: F[A]): ExtractOps[F, A] = new ExtractOps[F, A](fa)
+}
+
+final private[alleycats] class ExtractOps[F[_], A](private val fa: F[A]) extends AnyVal {
+  def extract(implicit F: Extract[F]): A = F.extract(fa)
+}

alleycats-core/src/test/scala/alleycats/SyntaxSuite.scala

@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2015 Typelevel
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package alleycats
+
+import cats.{Eq, Foldable}
+import alleycats.syntax.all.{catsSyntaxExtract, EmptyOps, ExtraFoldableOps}
+
+/**
+ * Test that our syntax implicits are working.
+ *
+ * Each method should correspond to one type class worth of syntax.
+ * Ideally, we should be testing every operator or method that we
+ * expect to add to generic parameters. This file is a safeguard
+ * against accidentally breaking (or removing) syntax which was
+ * otherwise untested.
+ *
+ * The strategy here is to create "mock" values of particular types,
+ * and then ensure that the syntax we want is available. We never plan
+ * to run any of these methods, so we don't need real values. All
+ * values in the methods should be generic -- we rely on parametricity
+ * to guarantee that the syntax will be available for any type with
+ * the proper type class instance(s).
+ *
+ * None of these tests should ever run, or do any runtime checks.
+ */
+object SyntaxSuite {
+
+  // pretend we have a value of type A
+  def mock[A]: A = ???
+
+  def testEmpty[A: Empty]: Unit = {
+    val x = mock[A]
+    implicit val y: Eq[A] = mock[Eq[A]]
+    val a0: Boolean = x.isEmpty
+    val a1: Boolean = x.nonEmpty
+  }
+
+  def testFoldable[F[_]: Foldable, A]: Unit = {
+    val x = mock[F[A]]
+    val y = mock[A => Unit]
+    x.foreach(y)
+  }
+
+  def testExtract[F[_]: Extract, A]: Unit = {
+    val x = mock[F[A]]
+    val y = x.extract
+  }
+}