Rename Id instances to idInstances to make selective import easier, f…

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

@@ -26,7 +26,7 @@ package object cats {
  * encodes pure unary function application.
  */
   type Id[A] = A
-  implicit val Id: Bimonad[Id] with Traverse[Id] =
+  implicit val idInstances: Bimonad[Id] with Traverse[Id] =
     new Bimonad[Id] with Traverse[Id] {
       def pure[A](a: A): A = a
       def extract[A](a: A): A = a

tests/src/test/scala/cats/tests/InjectTests.scala

@@ -41,13 +41,13 @@ class InjectTests extends CatsSuite {
 
   object Test1Interpreter extends (Test1Algebra ~> Id) {
     override def apply[A](fa: Test1Algebra[A]): Id[A] = fa match {
-      case Test1(k, h) => Id.pure[A](h(k))
+      case Test1(k, h) => h(k)
     }
   }
 
   object Test2Interpreter extends (Test2Algebra ~> Id) {
     override def apply[A](fa: Test2Algebra[A]): Id[A] = fa match {
-      case Test2(k, h) => Id.pure[A](h(k))
+      case Test2(k, h) => h(k)
     }
   }
 
@@ -65,7 +65,7 @@ class InjectTests extends CatsSuite {
             b <- Free.inject[Test2Algebra, F](Test2(y, identity))
           } yield a + b
         }
-      (res[T] foldMap coProductInterpreter) == Id.pure(x + y) should ===(true)
+      (res[T] foldMap coProductInterpreter) == (x + y) should ===(true)
     }
   }
 

tests/src/test/scala/cats/tests/NaturalTransformationTests.scala

@@ -29,11 +29,11 @@ class NaturalTransformationTests extends CatsSuite {
   case class Test2[A](v : A) extends Test2Algebra[A]
 
   object Test1NT extends (Test1Algebra ~> Id) {
-    override def apply[A](fa: Test1Algebra[A]): Id[A] = Id.pure(fa.v)
+    override def apply[A](fa: Test1Algebra[A]): Id[A] = fa.v
   }
 
   object Test2NT extends (Test2Algebra ~> Id) {
-    override def apply[A](fa: Test2Algebra[A]): Id[A] = Id.pure(fa.v)
+    override def apply[A](fa: Test2Algebra[A]): Id[A] = fa.v
   }
 
   type T[A] = Coproduct[Test1Algebra, Test2Algebra, A]
@@ -61,8 +61,8 @@ class NaturalTransformationTests extends CatsSuite {
   test("or") {
     val combinedInterpreter = Test1NT or Test2NT
     forAll { (a : Int, b : Int) =>
-      combinedInterpreter(Coproduct.left(Test1(a))) should === (Id.pure(a))
-      combinedInterpreter(Coproduct.right(Test2(b))) should === (Id.pure(b))
+      combinedInterpreter(Coproduct.left(Test1(a))) should === (a)
+      combinedInterpreter(Coproduct.right(Test2(b))) should === (b)
     }
   }
 }