Ported over from typelevel#409 by @ceedubs.

Originally was 9cb7319.
non · Aug 7, 2019 · 1089f71 · 1089f71
1 parent 1d25fcc
commit 1089f71
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Showing 2 changed files with 5 additions and 1 deletion.
diff --git a/src/main/scala/org/scalacheck/Arbitrary.scala b/src/main/scala/org/scalacheck/Arbitrary.scala
@@ -340,7 +340,7 @@ private[scalacheck] sealed trait ArbitraryLowPriority {
 
   /** Arbitrary instance of the Either type */
   implicit def arbEither[T, U](implicit at: Arbitrary[T], au: Arbitrary[U]): Arbitrary[Either[T, U]] =
-    Arbitrary(oneOf(arbitrary[T].map(Left(_)), arbitrary[U].map(Right(_))))
+    Arbitrary(Gen.either(at.arbitrary, au.arbitrary))
 
   /** Arbitrary instance of the Future type */
   implicit def arbFuture[T](implicit a: Arbitrary[T]): Arbitrary[Future[T]] =

diff --git a/src/main/scala/org/scalacheck/Gen.scala b/src/main/scala/org/scalacheck/Gen.scala
@@ -553,6 +553,10 @@ object Gen extends GenArities with GenVersionSpecific {
   def some[T](g: Gen[T]): Gen[Option[T]] =
     g.map(Some.apply)
 
+  /** Generates a `Left` of `T` or a `Right` of `U` with equal probability. */
+  def either[T, U](gt: Gen[T], gu: Gen[U]): Gen[Either[T, U]] =
+    oneOf(gt.map(Left(_)), gu.map(Right(_)))
+
   /** Chooses one of the given generators with a weighted random distribution */
   def frequency[T](gs: (Int, Gen[T])*): Gen[T] = {
     val filtered = gs.iterator.filter(_._1 > 0).toVector