Add opt-in AutoCloneType for Records (backport #2781) (#2785)

* Add opt-in AutoCloneType for Records (#2781)

There is a new trait, chisel3.experimental.AutoCloneType that is mixed
in to Bundle and can optionally be mixed in to user-defined Records. The
compiler plugin prints a deprecation warning on any user-defined
implementation of cloneType, telling the user to mix in AutoCloneType
before upgrading to 3.6.

(cherry picked from commit a234fd48ac8f5942c38fef5797292014e407b586)

# Conflicts:
#	core/src/main/scala/chisel3/Aggregate.scala
#	plugin/src/main/scala/chisel3/internal/plugin/BundleComponent.scala

* Resolve backport conflicts

* Do not make MixedVec extend AutoCloneType

It is a binary incompatible change that can wait for 3.6.

* Waive MiMa false positives

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

1 files changed, 41 insertions, 0 deletions

diff --git a/src/test/scala/chiselTests/AutoClonetypeSpec.scala b/src/test/scala/chiselTests/AutoClonetypeSpec.scala
index 5d2cd496..353ae58c 100644
--- a/src/test/scala/chiselTests/AutoClonetypeSpec.scala
+++ b/src/test/scala/chiselTests/AutoClonetypeSpec.scala
@@ -6,6 +6,8 @@ import chisel3._
 import chisel3.testers.TestUtils
 import chisel3.util.QueueIO
 import chisel3.stage.ChiselStage.elaborate
+import chisel3.experimental.AutoCloneType
+import scala.collection.immutable.ListMap
 
 class BundleWithIntArg(val i: Int) extends Bundle {
   val out = UInt(i.W)
@@ -72,6 +74,25 @@ class InheritingBundle extends QueueIO(UInt(8.W), 8) {
   val error = Output(Bool())
 }
 
+class RecordAutoCloneType[T <: Data](gen: T) extends Record with AutoCloneType {
+  lazy val elements = ListMap("value" -> gen)
+  // This is a weird thing to do, but as only Bundles have these methods, it should be legal
+  protected def _elementsImpl: Iterable[(String, Any)] = elements
+  protected def _usingPlugin = false
+}
+
+// Records that don't mixin AutoCloneType should still be able to implement the related methods
+// NOTE: This is a very weird thing to do, don't do it.
+class RecordWithVerbotenMethods(w: Int) extends Record {
+  lazy val elements = ListMap("value" -> UInt(w.W))
+  override def cloneType: this.type = (new RecordWithVerbotenMethods(w)).asInstanceOf[this.type]
+  // Verboten methods
+  protected def _usingPlugin = false
+  protected override def _cloneTypeImpl = this.cloneType
+
+  protected def _elementsImpl: Iterable[(String, Any)] = Nil
+}
+
 class AutoClonetypeSpec extends ChiselFlatSpec with Utils {
 
   "Bundles with Scala args" should "not need clonetype" in {
@@ -400,4 +421,24 @@ class AutoClonetypeSpec extends ChiselFlatSpec with Utils {
     }
     elaborate(new MyModule)
   }
+
+  it should "support Records that mixin AutoCloneType" in {
+    class MyModule extends Module {
+      val gen = new RecordAutoCloneType(UInt(8.W))
+      val in = IO(Input(gen))
+      val out = IO(Output(gen))
+      out := in
+    }
+    elaborate(new MyModule)
+  }
+
+  it should "support Records that don't mixin AutoCloneType and use forbidden methods" in {
+    class MyModule extends Module {
+      val gen = new RecordWithVerbotenMethods(8)
+      val in = IO(Input(gen))
+      val out = IO(Output(gen))
+      out := in
+    }
+    elaborate(new MyModule)
+  }
 }