Add CaseClass and SingletonObject type classes

Author: cvogt

project/Build.scala

@@ -19,7 +19,7 @@ object MyBuild extends Build{
  //scalacOptions ++= Seq("-Xprint:patmat", "-Xshow-phases"),
  testOptions in Test += Tests.Argument(TestFrameworks.ScalaTest, "-oFD"),
  parallelExecution := false, // <- until TMap thread-safety issues are resolved
- version := "0.5.0",
+ version := "0.5.1",
  organizationName := "Jan Christopher Vogt",
  organization := "org.cvogt",
  scalacOptions in (Compile, doc) <++= (version,sourceDirectory in Compile,name).map((v,src,n) => Seq(

readme.txt

@@ -4,6 +4,7 @@ http://cvogt.org/scala-extensions/
 Contents:
 
 Type-level constraints (org.cvogt.constraints)
+- CaseClass and SingletonObject type classes
 - Comparisons: <:<, =:=, >:>, !=:=, !<:<, !>:>, e.g. String !=:= And
 - Boolean Algebra: True, False, ==, !, &&, ||, Implies, Xor
 - Subset tests: In, NotIn, e.g. Int NotIn (Any,AnyRef,AnyVal)

src/main/scala/constraint.scala

@@ -38,3 +38,43 @@ object !=:={
  implicit def prove[Left,Right](implicit ev: ![Left =:= ${Right}]) = new !=:=[Left,Right]
 }
 */
+
+import scala.reflect.macros.blackbox
+import scala.language.experimental.macros
+
+/**
+Type class for case classes
+*/
+final class CaseClass[T]
+object CaseClass{
+ def checkCaseClassMacro[T:c.WeakTypeTag](c: blackbox.Context) = {
+ import c.universe._
+ val T = c.weakTypeOf[T]
+ if(
+ !T.typeSymbol.isClass || !T.typeSymbol.asClass.isCaseClass
+ ) c.error(c.enclosingPosition,s"$T does not have case modifier")
+ q"new _root_.org.cvogt.scala.constraint.CaseClass[$T]"
+ }
+ /**
+ fails compilation if T is not a case class
+ meaning this can be used as an implicit to check
+ */
+ implicit def checkCaseClass[T]: CaseClass[T] = macro checkCaseClassMacro[T]
+}
+
+final class SingletonObject[T]
+object SingletonObject{
+ def checkSingletonObjectMacro[T:c.WeakTypeTag](c: blackbox.Context) = {
+ import c.universe._
+ val T = c.weakTypeOf[T]
+ if(
+ !T.typeSymbol.isClass || !T.typeSymbol.asClass.isModuleClass
+ ) c.error(c.enclosingPosition,s"$T is not an object")
+ q"new _root_.org.cvogt.scala.constraint.SingletonObject[$T]"
+ }
+ /**
+ fails compilation if T is not a singleton object class
+ meaning this can be used as an implicit to check
+ */
+ implicit def checkSingletonObject[T]: SingletonObject[T] = macro checkSingletonObjectMacro[T]
+}

src/test/scala/constraint.scala

@@ -8,7 +8,10 @@ import org.cvogt.scala.constraint._
 trait A
 trait B extends A
 trait C
-
+class ANonCaseClass(i: Int)
+case class ACaseClass(i: Int)
+case object ACaseObject
+object ANonCaseObject
 class ConstraintTest extends FunSuite{
  test("<:<"){
  implicitly[A <:< A]
@@ -71,4 +74,14 @@ class ConstraintTest extends FunSuite{
  implicitly[Nothing !=:= String]
  implicitly[Nothing !=:= Int]
  }
+ test("CaseClass and SingletonObject type classes"){
+ implicitly[CaseClass[ACaseClass]]
+ assertTypeError("implicitly[CaseClass[ANonCaseClass]]")
+ implicitly[CaseClass[ACaseObject.type]]
+ assertTypeError("implicitly[CaseClass[ANonCaseObject.type]]")
+ assertTypeError("implicitly[SingletonObject[ACaseClass]]")
+ assertTypeError("implicitly[SingletonObject[ANonCaseClass]]")
+ implicitly[SingletonObject[ACaseObject.type]]
+ implicitly[SingletonObject[ANonCaseObject.type]]
+ }
 }