Merge pull request #4733 from danicheg/empty-option-instance

danicheg · web-flow · commit 726be059c8f6 · 2025-03-30T10:19:34.000+03:00
Add the `Empty[Option[A]]` instance in alleycats
diff --git a/alleycats-core/src/main/scala/alleycats/Empty.scala b/alleycats-core/src/main/scala/alleycats/Empty.scala
@@ -77,7 +77,10 @@ object Empty extends EmptyInstances0 {
 
 }
 
-private[alleycats] trait EmptyInstances0 extends compat.IterableEmptyInstance with EmptyInstances1
+private[alleycats] trait EmptyInstances0 extends compat.IterableEmptyInstance with EmptyInstances1 {
+  private[this] val emptyOptionSingleton: Empty[Option[Nothing]] = Empty(None)
+  implicit def alleycatsEmptyForOption[A]: Empty[Option[A]] = emptyOptionSingleton.asInstanceOf[Empty[Option[A]]]
+}
 
 private[alleycats] trait EmptyInstances1 extends EmptyInstances2 {
   // If Monoid extended Empty then this could be an exported subclass instance provided by Monoid

Original file line number	Diff line number	Diff line change
`@@ -77,7 +77,10 @@ object Empty extends EmptyInstances0 {`
`77`	`77`
`78`	`78`	`}`
`79`	`79`
`80`		`-private[alleycats] trait EmptyInstances0 extends compat.IterableEmptyInstance with EmptyInstances1`
	`80`	`+private[alleycats] trait EmptyInstances0 extends compat.IterableEmptyInstance with EmptyInstances1 {`
	`81`	`+ private[this] val emptyOptionSingleton: Empty[Option[Nothing]] = Empty(None)`
	`82`	`+ implicit def alleycatsEmptyForOption[A]: Empty[Option[A]] = emptyOptionSingleton.asInstanceOf[Empty[Option[A]]]`
	`83`	`+}`
`81`	`84`
`82`	`85`	`private[alleycats] trait EmptyInstances1 extends EmptyInstances2 {`
`83`	`86`	`// If Monoid extended Empty then this could be an exported subclass instance provided by Monoid`