added liftTo to Try Either and Option (#2179)

core/src/main/scala/cats/ApplicativeError.scala

@@ -180,4 +180,30 @@ trait ApplicativeError[F[_], E] extends Applicative[F] {
 
 object ApplicativeError {
   def apply[F[_], E](implicit F: ApplicativeError[F, E]): ApplicativeError[F, E] = F
+
+  private[cats] final class LiftFromOptionPartially[F[_]](val dummy: Boolean = true) extends AnyVal {
+    def apply[E, A](oa: Option[A], ifEmpty: => E)(implicit F: ApplicativeError[F, E]): F[A] =
+      oa match {
+        case Some(a) => F.pure(a)
+        case None => F.raiseError(ifEmpty)
+      }
+  }
+
+
+  /**
+    * lift from scala.Option[A] to a F[A]
+    *
+    * Example:
+    * {{{
+    * scala> import cats.implicits._
+    * scala> import cats.ApplicativeError
+    *
+    * scala> ApplicativeError.liftFromOption[Either[String, ?]](Some(1), "Empty")
+    * res0: scala.Either[String, Int] = Right(1)
+    *
+    * scala> ApplicativeError.liftFromOption[Either[String, ?]](Option.empty[Int], "Empty")
+    * res1: scala.Either[String, Int] = Left(Empty)
+    * }}}
+    */
+  def liftFromOption[F[_]]: LiftFromOptionPartially[F] = new LiftFromOptionPartially[F]
 }

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

@@ -0,0 +1,32 @@
+package cats
+package syntax
+
+import scala.util.Try
+
+trait TrySyntax {
+  implicit final def catsSyntaxTry[A](t: Try[A]): TryOps[A] = new TryOps(t)
+}
+
+
+final class TryOps[A](val self: Try[A]) extends AnyVal {
+
+  /**
+    * lift the `try` into a `F[_]` with `ApplicativeError[F, Throwable]` instance
+    *
+    * {{{
+    * scala> import cats.implicits._
+    * scala> import util.Try
+    *
+    * scala> val s: Try[Int] = Try(3)
+    * scala> s.liftTo[Either[Throwable, ?]]
+    * res0: Either[Throwable, Int] = Right(3)
+    *
+    * scala> val f: Try[Int] = Try(throw new Throwable("boo"))
+    * scala> f.liftTo[Either[Throwable, ?]]
+    * res0: Either[Throwable, Int] = Left(java.lang.Throwable: boo)
+    * }}}
+    */
+  def liftTo[F[_]](implicit F: ApplicativeError[F, Throwable]): F[A] =
+    F.fromTry(self)
+
+}

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

@@ -55,3 +55,5 @@ trait AllSyntax
 
 trait AllSyntaxBinCompat0
     extends UnorderedTraverseSyntax
+    with ApplicativeErrorExtension
+    with TrySyntax

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

@@ -11,6 +11,39 @@ trait ApplicativeErrorSyntax {
     new ApplicativeErrorOps[F, E, A](fa)
 }
 
+/**
+  * Extension to ApplicativeError in a binary compat way
+  */
+trait ApplicativeErrorExtension {
+  implicit final def catsSyntaxApplicativeErrorExtension[F[_], E](F: ApplicativeError[F, E]):
+    ApplicativeErrorExtensionOps[F, E] =
+      new ApplicativeErrorExtensionOps(F)
+}
+
+final class ApplicativeErrorExtensionOps[F[_], E](F: ApplicativeError[F, E]) {
+
+
+  /**
+    * Convert from scala.Option
+    *
+    * Example:
+    * {{{
+    * scala> import cats.implicits._
+    * scala> import cats.ApplicativeError
+    * scala> val F = ApplicativeError[Either[String, ?], String]
+    *
+    * scala> F.fromOption(Some(1), "Empty")
+    * res0: scala.Either[String, Int] = Right(1)
+    *
+    * scala> F.fromOption(Option.empty[Int], "Empty")
+    * res1: scala.Either[String, Int] = Left(Empty)
+    * }}}
+    */
+  def fromOption[A](oa: Option[A], ifEmpty: => E): F[A] =
+    ApplicativeError.liftFromOption(oa, ifEmpty)(F)
+
+}
+
 final class ApplicativeErrorIdOps[E](val e: E) extends AnyVal {
   def raiseError[F[_], A](implicit F: ApplicativeError[F, E]): F[A] =
     F.raiseError(e)

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

@@ -269,8 +269,21 @@ final class EitherOps[A, B](val eab: Either[A, B]) extends AnyVal {
   def raiseOrPure[F[_]](implicit ev: ApplicativeError[F, A]): F[B] =
     ev.fromEither(eab)
 
+  /**
+    * lift the `Either` into a `F[_]` with `ApplicativeError[F, A]` instance
+    *
+    * {{{
+    * scala> import cats.implicits._
+    * scala> import cats.data.EitherT
+    * scala> val e: Either[String, Int] = Right(3)
+    * scala> e.liftTo[EitherT[Option, String, ?]]
+    * res0: cats.data.EitherT[Option, String, Int] = EitherT(Some(Right(3)))
+    * }}}
+    */
+  def liftTo[F[_]](implicit F: ApplicativeError[F, A]): F[B] = F.fromEither(eab)
 }
 
+
 final class EitherObjectOps(val either: Either.type) extends AnyVal { // scalastyle:off ensure.single.space.after.token
   def left[A, B](a: A): Either[A, B] = Left(a)
 

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

@@ -2,6 +2,7 @@ package cats
 package syntax
 
 import cats.data.{Ior, Validated, ValidatedNel}
+import cats.syntax.OptionOps.LiftToPartiallyApplied
 
 trait OptionSyntax {
   final def none[A]: Option[A] = Option.empty[A]
@@ -170,4 +171,28 @@ final class OptionOps[A](val oa: Option[A]) extends AnyVal {
    * }}}
    */
   def orEmpty(implicit A: Monoid[A]): A = oa.getOrElse(A.empty)
+
+  /**
+    * Lift to a F[A] as long as it has an ApplicativeError[F] instance
+    *
+    * Example:
+    * {{{
+    * scala> import cats.implicits._
+    *
+    * scala> Some(1).liftTo[Either[String, ?]]("Empty")
+    * res0: scala.Either[String, Int] = Right(1)
+    *
+    * scala> Option.empty[Int].liftTo[Either[String, ?]]("Empty")
+    * res1: scala.Either[String, Int] = Left(Empty)
+    * }}}
+    */
+  def liftTo[F[_]]: LiftToPartiallyApplied[F, A] = new LiftToPartiallyApplied(oa)
+
+}
+
+object OptionOps {
+  private[syntax] final class LiftToPartiallyApplied[F[_], A](oa: Option[A]) {
+    def apply[E](ifEmpty: => E)(implicit F: ApplicativeError[F, E]): F[A] =
+      ApplicativeError.liftFromOption(oa, ifEmpty)
+  }
 }