add -Xsource:3 option

[xuwei-k]

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[github-actions]

diff --git a/org.atnos.site.CreateEffects.html b/org.atnos.site.CreateEffects.html
index a3f84f1..faedfc1 100644
--- a/org.atnos.site.CreateEffects.html
+++ b/org.atnos.site.CreateEffects.html
@@ -350,7 +350,7 @@ an Effect for a new “optional” type.</p>
 
     def runMaybe[R, U, A, B](effect: Eff[R, A])(implicit m: Member.Aux[Maybe, R, U]): Eff[U, Option[A]] =
       recurse(effect)(new Recurser[Maybe, U, A, Option[A]] {
-        def onPure(a: A) = Some(a)
+        def onPure(a: A): Option[A] = Some(a)
 
         def onEffect[X](m: Maybe[X]): X Either Eff[U, Option[A]] =
           m match {