Revert "adapt to scala/scala#7696"

SethTisue · SethTisue · commit fcf50933c087 · 2019-03-27T14:06:59.000+01:00
This reverts commit 17647af. the upstream change was reverted, so we revert this too also use latest Scala nightly
diff --git a/build.sbt b/build.sbt
@@ -5,7 +5,7 @@ version in ThisBuild := "0.1.3-SNAPSHOT"
 resolvers in ThisBuild += "scala-integration" at "https://scala-ci.typesafe.com/artifactory/scala-integration/"
 
 scalaVersionsByJvm in ThisBuild := {
-  val v213 = "2.13.0-pre-d645559"  // Feb 27
+  val v213 = "2.13.0-pre-eb074a8"  // Mar 27
   Map(
     8 -> List(v213 -> true),
     11 -> List(v213 -> false),
diff --git a/core/src/main/scala/scala/collection/immutable/OldHashSet.scala b/core/src/main/scala/scala/collection/immutable/OldHashSet.scala
@@ -50,7 +50,7 @@ sealed abstract class OldHashSet[A]
       super.subsetOf(that)
   }
 
-  override def concat(that: collection.IterableOnce[A])(implicit dummy: DummyImplicit): OldHashSet[A] = that match {
+  override def concat(that: collection.IterableOnce[A]): OldHashSet[A] = that match {
     case that: OldHashSet[A] =>
       val buffer = new Array[OldHashSet[A]](bufferSize(this.size + that.size))
       nullToEmpty(union0(that, 0, buffer, 0))

Original file line number	Diff line number	Diff line change
`@@ -50,7 +50,7 @@ sealed abstract class OldHashSet[A]`
`50`	`50`	`super.subsetOf(that)`
`51`	`51`	`}`
`52`	`52`
`53`		`- override def concat(that: collection.IterableOnce[A])(implicit dummy: DummyImplicit): OldHashSet[A] = that match {`
	`53`	`+ override def concat(that: collection.IterableOnce[A]): OldHashSet[A] = that match {`
`54`	`54`	`case that: OldHashSet[A] =>`
`55`	`55`	`val buffer = new Array[OldHashSet[A]](bufferSize(this.size + that.size))`
`56`	`56`	`nullToEmpty(union0(that, 0, buffer, 0))`