[2.13] explicitly use a parallel vector

2 files changed, 10 insertions, 2 deletions

diff --git a/build.sbt b/build.sbt
index 616bcbd2..b2874ae6 100644
--- a/build.sbt
+++ b/build.sbt
@@ -52,6 +52,13 @@ lazy val commonSettings = Seq(
     "org.json4s" %% "json4s-native" % "3.6.8",
     "org.apache.commons" % "commons-text" % "1.8"
   ),
+  // starting with scala 2.13 the parallel collections are separate from the standard library
+  libraryDependencies ++= {
+    CrossVersion.partialVersion(scalaVersion.value) match {
+      case Some((2, major)) if major <= 12 => Seq()
+      case _ => Seq("org.scala-lang.modules" %% "scala-parallel-collections" % "0.2.0")
+    }
+  },
   resolvers ++= Seq(
     Resolver.sonatypeRepo("snapshots"),
     Resolver.sonatypeRepo("releases")
diff --git a/src/main/scala/firrtl/stage/phases/Compiler.scala b/src/main/scala/firrtl/stage/phases/Compiler.scala
index d5c45dba..66dad55e 100644
--- a/src/main/scala/firrtl/stage/phases/Compiler.scala
+++ b/src/main/scala/firrtl/stage/phases/Compiler.scala
@@ -111,8 +111,9 @@ class Compiler extends Phase with Translator[AnnotationSeq, Seq[CompilerRun]] {
       c.copy(stateOut = Some(annotationsOut))
     }
 
-    if (b.size <= 1) { b.map(f)         }
-    else             { b.par.map(f).seq }
+    if (b.size <= 1) { b.map(f) } else {
+      collection.parallel.immutable.ParVector(b :_*).par.map(f).seq
+    }
   }
 
   private def compilerToTransforms(a: FirrtlCompiler): Seq[TransformDependency] = a match {