Merge pull request #12 from propensive/ruippeixotog-cats-contravariant-example

Ruippeixotog cats contravariant example

6 files changed, 52 insertions, 51 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e7f1455
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+target
+.jvm
+.js
+.native
diff --git a/build.sbt b/build.sbt
index db54f76..33026f3 100644
--- a/build.sbt
+++ b/build.sbt
@@ -23,6 +23,7 @@ lazy val examples = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .settings(publishSettings: _*)
   .settings(moduleName := "magnolia-examples")
   .settings(quasiQuotesDependencies)
+  .settings(examplesDependencies)
   .nativeSettings(nativeSettings)
   .dependsOn(core)
 
@@ -132,6 +133,9 @@ lazy val scalaMacroDependencies: Seq[Setting[_]] = Seq(
   libraryDependencies += compilerPlugin("org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full)
 )
 
+lazy val examplesDependencies: Seq[Setting[_]] = Seq(
+  libraryDependencies += "org.typelevel" %% "cats-core" % "0.9.0")
+
 credentials ++= (for {
   username <- Option(System.getenv().get("SONATYPE_USERNAME"))
   password <- Option(System.getenv().get("SONATYPE_PASSWORD"))
diff --git a/core/src/main/scala/magnolia.scala b/core/src/main/scala/magnolia.scala
index 66d59d0..e2d1341 100644
--- a/core/src/main/scala/magnolia.scala
+++ b/core/src/main/scala/magnolia.scala
@@ -221,8 +221,8 @@ class Macros(val c: whitebox.Context) {
     val contraDerivationType = appliedType(contraDerivationTypeclass, List(typeConstructor))
     val contraDerivation2Type = appliedType(contraDerivation2Typeclass, List(typeConstructor))
 
-    def findDerivationImplicit[T <: DerivationImplicit](tpe: c.Type, cons: Tree => T): Try[DerivationImplicit] =
-      Try(cons(c.untypecheck(c.inferImplicitValue(tpe, false, false))))
+    def findDerivationImplicit[T <: DerivationImplicit](derivationType: c.Type, wrap: Tree => T): Try[DerivationImplicit] =
+      Try(wrap(c.untypecheck(c.inferImplicitValue(derivationType, false, false))))
 
     val derivationImplicit =
       findDerivationImplicit(coDerivationType, CovariantDerivationImplicit)
@@ -258,17 +258,12 @@ class Macros(val c: whitebox.Context) {
           val searchType = appliedType(typeConstructor, genericType)
           Some(q"_root_.magnolia.Lazy[$searchType]($methodAsString)")
       }
-    } else {
-      directInferImplicit(genericType, typeConstructor, derivationImplicit)
-    }
+    } else directInferImplicit(genericType, typeConstructor, derivationImplicit)
    
-    if(currentStack.frames.isEmpty) recursionStack = Map()
+    if(currentStack.frames.isEmpty) recursionStack = ListMap()
 
     result.map { tree =>
-      if(currentStack.frames.isEmpty) {
-        val res = c.untypecheck(removeLazy.transform(tree))
-        res
-      } else tree
+      if(currentStack.frames.isEmpty) c.untypecheck(removeLazy.transform(tree)) else tree
     }.getOrElse {
       c.abort(c.enclosingPosition, "could not infer typeclass for type $genericType")
     }
@@ -312,8 +307,8 @@ private[magnolia] object CompileTimeState {
     def termName(c: whitebox.Context): c.TermName = term.asInstanceOf[c.TermName]
   }
 
-  private[magnolia] var recursionStack: Map[api.Position, Stack] =
-    Map()
+  private[magnolia] var recursionStack: ListMap[api.Position, Stack] =
+    ListMap()
   
   private[magnolia] var emittedErrors: Set[ImplicitNotFound] = Set()
 }
diff --git a/examples/src/main/scala/cats.scala b/examples/src/main/scala/cats.scala
new file mode 100644
index 0000000..8d33a0f
--- /dev/null
+++ b/examples/src/main/scala/cats.scala
@@ -0,0 +1,22 @@
+package magnolia.examples
+
+import scala.collection.immutable.ListMap
+import scala.language.experimental.macros
+
+import cats.Show
+import magnolia.ContravariantDerivation
+import magnolia.Macros
+
+object catsShowDerivation {
+
+  implicit val showDerivation: ContravariantDerivation[Show] =
+    new ContravariantDerivation[Show] {
+      type Return = String
+      def call[T](show: Show[T], value: T): String = show.show(value)
+      def construct[T](body: T => String): Show[T] = body(_)
+      def join(xs: ListMap[String, String]): String =
+        xs.map { case (k, v) => s"$k=$v" }.mkString("{", ", ", "}")
+    }
+  
+  implicit def genericShow[T]: Show[T] = macro Macros.magnolia[T, Show[_]]
+}
diff --git a/examples/src/main/scala/example.scala b/examples/src/main/scala/eq.scala
index 543fa3d..30e7869 100644
--- a/examples/src/main/scala/example.scala
+++ b/examples/src/main/scala/eq.scala
@@ -3,25 +3,19 @@ package magnolia.examples
 import magnolia._
 
 import language.experimental.macros
-import language.higherKinds
 import collection.immutable.ListMap
 
 object `package` {
-  implicit class Showable[T: Show](t: T) {
-    def show: String = implicitly[Show[T]].show(t)
-  }
-  implicit val showString: Show[String] = identity
-  implicit val showBool: Show[Boolean] = _.toString
-  implicit def showList[T: Show]: Show[List[T]] = xs => xs.map { x => s"list:${implicitly[Show[T]].show(x)}" }.mkString(";")
-  implicit def showSet[T: Show]: Show[Set[T]] = s => "set"
-
   implicit class Equable[T: Eq](t: T) {
     def isEqualTo(other: T): Boolean = implicitly[Eq[T]].isEqual(t, other)
   }
+  
   implicit val eqString: Eq[String] = _ == _
   implicit val eqBool: Eq[Boolean] = _ == _
+  
   implicit def eqList[T: Eq]: Eq[List[T]] =
     (l1, l2) => l1.size == l2.size && (l1 zip l2).forall { case (e1, e2) => e1 isEqualTo e2 }
+
   implicit def eqSet[T: Eq]: Eq[Set[T]] =
     (s1, s2) => s1.size == s2.size && (s1 zip s2).forall { case (e1, e2) => e1 isEqualTo e2 }
 }
@@ -36,37 +30,21 @@ case class Organization(name: String, contacts: Set[Person]) extends Entity
 case class Address(lines: List[String], country: Country)
 case class Country(name: String, code: String, salesTax: Boolean)
 
-trait Show[T] { def show(t: T): String }
-object Show extends Show_1 {
-  implicit val showInt: Show[Int] = _.toString
-  implicit val derivation = new ContravariantDerivation[Show] {
-    type Return = String
-    def call[T](show: Show[T], value: T): String = show.show(value)
-    def construct[T](body: T => String): Show[T] = body(_)
-    def join(xs: ListMap[String, String]): String = xs.map { case (k, v) => s"$k=$v" }.mkString("{", ", ", "}")
-  }
-}
-
-trait Show_1 {
-  implicit def generic[T]: Show[T] = macro Macros.magnolia[T, Show[_]]
-}
-
 trait Eq[T] { def isEqual(a: T, b: T): Boolean }
 
-object Eq extends Eq_1 {
+object Eq {
 
   implicit val eqInt: Eq[Int] = _ == _
 
-  implicit val derivation = new ContravariantDerivation2[Eq] {
+  implicit val derivation: ContravariantDerivation2[Eq] = new ContravariantDerivation2[Eq] {
     type Return = Boolean
+    
     def call[T](eq: Eq[T], value1: T, value2: T): Boolean =
       if(value1.getClass == value2.getClass) eq.isEqual(value1, value2) else false
+    
     def construct[T](body: (T, T) => Boolean): Eq[T] = body(_, _)
     def join(elements: ListMap[String, Boolean]): Boolean = elements.forall(_._2)
   }
-}
-
-trait Eq_1 {
+  
   implicit def generic[T]: Eq[T] = macro Macros.magnolia[T, Eq[_]]
 }
-
diff --git a/tests/shared/src/main/scala/magnolia/main.scala b/tests/shared/src/main/scala/magnolia/main.scala
index 3ac3fb6..c6cd9bc 100644
--- a/tests/shared/src/main/scala/magnolia/main.scala
+++ b/tests/shared/src/main/scala/magnolia/main.scala
@@ -1,23 +1,21 @@
 package magnolia
 
-import examples._
+import examples.{Address, Branch, Country, Entity, Leaf, Person}
+import cats.instances.all._
+import cats.syntax.all._
+import examples.catsShowDerivation._
+import language.experimental.macros
 
 object Main {
-  def main(args: Array[String]): Unit = {
 
-    val tree1: Tree = Branch(Branch(Leaf(1), Leaf(2)), Leaf(3))
-    val tree2: Tree = Branch(Leaf(1), Leaf(2))
+  def main(args: Array[String]): Unit = {
+    val tree1 = Branch(Branch(Leaf(1), Leaf(2)), Leaf(3))
 
     println(tree1.show)
     println(tree1 isEqualTo tree1)
-    println(tree1 isEqualTo tree2)
 
-    println(Branch(Branch(Leaf(1), Leaf(2)), Leaf(3)).show)
-    
     println(List[Entity](Person("John Smith",
       Address(List("1 High Street", "London", "SW1A 1AA"),
         Country("UK", "GBR", false)))).show)
-
   }
 }
-