Add syntax for validated.

core/src/main/scala/cats/syntax/all.scala

@@ -30,3 +30,4 @@ trait AllSyntax
     with StrongSyntax
     with TraverseSyntax
     with XorSyntax
+    with ValidatedSyntax

core/src/main/scala/cats/syntax/option.scala

@@ -1,7 +1,7 @@
 package cats
 package syntax
 
-import cats.data.Xor
+import cats.data.{ Xor, Validated, ValidatedNel }
 
 trait OptionSyntax {
   def none[A] = Option.empty[A]
@@ -16,5 +16,9 @@ class OptionIdOps[A](val a: A) extends AnyVal {
 class OptionOps[A](val oa: Option[A]) extends AnyVal {
   def toLeftXor[B](b: => B): A Xor B = oa.fold[A Xor B](Xor.Right(b))(Xor.Left(_))
   def toRightXor[B](b: => B): B Xor A = oa.fold[B Xor A](Xor.Left(b))(Xor.Right(_))
+  def toInvalid[B](b: => B): Validated[A, B] = oa.fold[Validated[A, B]](Validated.Valid(b))(Validated.Invalid(_))
+  def toInvalidNel[B](b: => B): ValidatedNel[A, B] = oa.fold[ValidatedNel[A, B]](Validated.Valid(b))(Validated.invalidNel(_))
+  def toValid[B](b: => B): Validated[B, A] = oa.fold[Validated[B, A]](Validated.Invalid(b))(Validated.Valid(_))
+  def toValidNel[B](b: => B): ValidatedNel[B, A] = oa.fold[ValidatedNel[B, A]](Validated.invalidNel(b))(Validated.Valid(_))
   def orEmpty(implicit A: Monoid[A]): A = oa.getOrElse(A.empty)
 }

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

@@ -28,4 +28,5 @@ package object syntax {
   object strong extends StrongSyntax
   object traverse extends TraverseSyntax
   object xor extends XorSyntax
+  object validated extends ValidatedSyntax
 }

core/src/main/scala/cats/syntax/validated.scala

@@ -0,0 +1,15 @@
+package cats
+package syntax
+
+import cats.data.{ Validated, ValidatedNel }
+
+trait ValidatedSyntax {
+  implicit def validatedIdSyntax[A](a: A): ValidatedIdSyntax[A] = new ValidatedIdSyntax(a)
+}
+
+class ValidatedIdSyntax[A](val a: A) extends AnyVal {
+  def valid[B]: Validated[B, A] = Validated.Valid(a)
+  def validNel[B]: ValidatedNel[B, A] = Validated.Valid(a)
+  def invalid[B]: Validated[A, B] = Validated.Invalid(a)
+  def invalidNel[B]: ValidatedNel[A, B] = Validated.invalidNel(a)
+}