Strong enums

chiselFrontend/src/main/scala/chisel3/core/Bits.scala

@@ -19,7 +19,7 @@ import chisel3.internal.firrtl.PrimOp._
   *
   * @define coll element
   */
-abstract class Element(private[chisel3] val width: Width) extends Data {
+abstract class Element extends Data {
   private[chisel3] override def bind(target: Binding, parentDirection: SpecifiedDirection) {
     binding = target
     val resolvedDirection = SpecifiedDirection.fromParent(parentDirection, specifiedDirection)
@@ -69,7 +69,7 @@ private[chisel3] sealed trait ToBoolable extends Element {
   * @define sumWidth       @note The width of the returned $coll is `width of this` + `width of that`.
   * @define unchangedWidth @note The width of the returned $coll is unchanged, i.e., the `width of this`.
   */
-sealed abstract class Bits(width: Width) extends Element(width) with ToBoolable { //scalastyle:off number.of.methods
+sealed abstract class Bits(private[chisel3] val width: Width) extends Element with ToBoolable { //scalastyle:off number.of.methods
   // TODO: perhaps make this concrete?
   // Arguments for: self-checking code (can't do arithmetic on bits)
   // Arguments against: generates down to a FIRRTL UInt anyways
@@ -1693,7 +1693,7 @@ object FixedPoint {
   *
   * @note This API is experimental and subject to change
   */
-final class Analog private (width: Width) extends Element(width) {
+final class Analog private (private[chisel3] val width: Width) extends Element {
   require(width.known, "Since Analog is only for use in BlackBoxes, width must be known")
 
   private[core] override def typeEquivalent(that: Data): Boolean =

chiselFrontend/src/main/scala/chisel3/core/Clock.scala

@@ -12,7 +12,7 @@ object Clock {
 }
 
 // TODO: Document this.
-sealed class Clock extends Element(Width(1)) {
+sealed class Clock(private[chisel3] val width: Width = Width(1)) extends Element {
   def cloneType: this.type = Clock().asInstanceOf[this.type]
 
   private[core] def typeEquivalent(that: Data): Boolean =

chiselFrontend/src/main/scala/chisel3/core/Data.scala

@@ -529,10 +529,12 @@ object WireInit {
 /** RHS (source) for Invalidate API.
   * Causes connection logic to emit a DefInvalid when connected to an output port (or wire).
   */
-object DontCare extends Element(width = UnknownWidth()) {
+object DontCare extends Element {
   // This object should be initialized before we execute any user code that refers to it,
   //  otherwise this "Chisel" object will end up on the UserModule's id list.
 
+  private[chisel3] override val width: Width = UnknownWidth()
+
   bind(DontCareBinding(), SpecifiedDirection.Output)
   override def cloneType = DontCare
 

chiselFrontend/src/main/scala/chisel3/core/MonoConnect.scala

@@ -79,6 +79,12 @@ object MonoConnect {
         elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
       case (sink_e: Clock, source_e: Clock) =>
         elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: EnumType, source_e: UnsafeEnum) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: EnumType, source_e: EnumType) if sink_e.getClass.equals(source_e.getClass) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
+      case (sink_e: UnsafeEnum, source_e: UInt) =>
+        elemConnect(sourceInfo, connectCompileOptions, sink_e, source_e, context_mod)
 
       // Handle Vec case
       case (sink_v: Vec[Data @unchecked], source_v: Vec[Data @unchecked]) =>