fix dotty warnings

Author: giabao

build.sbt

@@ -36,6 +36,7 @@ libraryDependencies ++= Seq(
   "org.scalatest" %% "scalatest" % "3.1.1",
   "junit" % "junit" % "4.12"
 )
+Test / scalacOptions ++= (if (isDotty.value) Seq("-language:implicitConversions") else Nil)
 
 import scala.xml.{Node => XmlNode, NodeSeq => XmlNodeSeq, _}
 import scala.xml.transform.{RewriteRule, RuleTransformer}

src/main/scala/org/scalatestplus/junit/JUnitHelper.scala

@@ -23,7 +23,7 @@ import org.scalatest.{Suite, TagAnnotation}
 private[junit] object JUnitHelper {
 
   def mergeMap[A, B](ms: List[Map[A, B]])(f: (B, B) => B): Map[A, B] =
-    (Map[A, B]() /: (for (m <- ms; kv <- m) yield kv)) { (a, kv) =>
+    (for (m <- ms; kv <- m) yield kv).foldLeft(Map[A, B]()) { (a, kv) =>
       a + (if (a.contains(kv._1)) kv._1 -> f(a(kv._1), kv._2) else kv)
     }
 

src/test/scala/org/scalatestplus/junit/JUnitSuiteSuite.scala

@@ -15,15 +15,15 @@
  */
 package org.scalatestplus.junit {
 
-  import org.scalatest._
+import org.scalatest._
 import org.scalatest.events._
 
   // Put fixture suites in a subpackage, so they won't be discovered by
   // -m org.scalatest.junit when running the test target for this project.
   package helpers {
 
     import _root_.org.junit.Ignore
-import _root_.org.junit.Test
+    import _root_.org.junit.Test
 
     class HappySuite extends JUnitSuite {