Switch to using experimental trait for OpaqueTypes (backport #2783) (#2836)

* Switch to using experimental trait for OpaqueTypes (#2783)

This makes it more clear that the feature is experimental. Users may
still override the opaqueType method for more dynamic control over when
instances of a given Record are OpaqueTypes or not, but they are
discouraged from doing so.

(cherry picked from commit 7525dc71ccc2050d8e4a68b38f3b76920ba693fc)

* Fix cloneType in RecordSpec

Co-authored-by: Jack Koenig <koenig@sifive.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/test/scala/chiselTests/Direction.scala b/src/test/scala/chiselTests/Direction.scala
index 03755e83..642a507c 100644
--- a/src/test/scala/chiselTests/Direction.scala
+++ b/src/test/scala/chiselTests/Direction.scala
@@ -4,6 +4,7 @@ package chiselTests
 
 import org.scalatest._
 import chisel3._
+import chisel3.experimental.OpaqueType
 import chisel3.stage.ChiselStage
 import org.scalatest.matchers.should.Matchers
 
@@ -370,10 +371,9 @@ class DirectionSpec extends ChiselPropSpec with Matchers with Utils {
       val valid = Bool()
       val ready = Flipped(Bool())
     }
-    class MyOpaqueType extends Record {
+    class MyOpaqueType extends Record with OpaqueType {
       val k = new Decoupled()
       val elements = SeqMap("" -> k)
-      override def opaqueType = elements.size == 1
       override def cloneType: this.type = (new MyOpaqueType).asInstanceOf[this.type]
     }
     class MyModule extends RawModule {