2 files changed, 19 insertions, 11 deletions

diff --git a/chiselFrontend/src/main/scala/chisel3/core/Aggregate.scala b/chiselFrontend/src/main/scala/chisel3/core/Aggregate.scala
index fa69bef0..4b35c163 100644
--- a/chiselFrontend/src/main/scala/chisel3/core/Aggregate.scala
+++ b/chiselFrontend/src/main/scala/chisel3/core/Aggregate.scala
@@ -473,6 +473,8 @@ abstract class Record(private[chisel3] implicit val compileOptions: CompileOptio
   def toPrintable: Printable = toPrintableHelper(elements.toList)
 }
 
+class AutoClonetypeException(message: String) extends ChiselException(message, null)
+
 /** Base class for data types defined as a bundle of other data types.
   *
   * Usage: extend this class (either as an anonymous or named class) and define
@@ -566,16 +568,15 @@ class Bundle(implicit compileOptions: CompileOptions) extends Record {
     // This attempts to infer constructor and arguments to clone this Bundle subtype without
     // requiring the user explicitly overriding cloneType.
     import scala.language.existentials
+    import scala.reflect.runtime.universe._
+
+    val clazz = this.getClass
 
     def reflectError(desc: String): Nothing = {
-      Builder.exception(s"Unable to automatically infer cloneType on $this: $desc").asInstanceOf[Nothing]
+      throw new AutoClonetypeException(s"Unable to automatically infer cloneType on $clazz: $desc")
     }
 
-    import scala.reflect.runtime.universe._
-
     // Check if this is an inner class, and if so, try to get the outer instance
-    val clazz = this.getClass
-
     val outerClassInstance = Option(clazz.getEnclosingClass).map { outerClass =>
       def canAssignOuterClass(x: Object) = outerClass.isAssignableFrom(x.getClass)
 
@@ -632,7 +633,7 @@ class Bundle(implicit compileOptions: CompileOptions) extends Record {
         case Some(clone) =>
           clone._outerInst = this._outerInst
           if (!clone.typeEquivalent(this)) {
-            reflectError(s"Automatically cloned $clone not type-equivalent to base $this." +
+            reflectError(s"automatically cloned $clone not type-equivalent to base." +
             " Constructor argument values were not inferred, ensure constructor is deterministic.")
           }
           return clone.asInstanceOf[this.type]
@@ -645,7 +646,7 @@ class Bundle(implicit compileOptions: CompileOptions) extends Record {
     val classSymbol = try {
       mirror.reflect(this).symbol
     } catch {
-      case e: scala.reflect.internal.Symbols#CyclicReference => reflectError(s"Scala cannot reflect on $this, got exception $e." +
+      case e: scala.reflect.internal.Symbols#CyclicReference => reflectError(s"got exception $e attempting Scala reflection." +
           " This is known to occur with inner classes on anonymous outer classes." +
           " In those cases, autoclonetype only works with no-argument constructors, or you can define a custom cloneType.")
     }
@@ -679,7 +680,7 @@ class Bundle(implicit compileOptions: CompileOptions) extends Record {
         return clone
       } catch {
         case e @ (_: java.lang.reflect.InvocationTargetException | _: IllegalArgumentException) =>
-          reflectError(s"Unexpected failure at constructor invocation, got $e.")
+          reflectError(s"unexpected failure at constructor invocation, got $e.")
       }
     }
 
@@ -698,7 +699,7 @@ class Bundle(implicit compileOptions: CompileOptions) extends Record {
     val accessorsName = accessors.filter(_.isStable).map(_.name.toString)
     val paramsDiff = ctorParamsNames.toSet -- accessorsName.toSet
     if (!paramsDiff.isEmpty) {
-      reflectError(s"constructor has parameters $paramsDiff that are not both immutable and accessible." +
+      reflectError(s"constructor has parameters (${paramsDiff.toList.sorted.mkString(", ")}) that are not both immutable and accessible." +
           " Either make all parameters immutable and accessible (vals) so cloneType can be inferred, or define a custom cloneType method.")
     }
 
@@ -716,7 +717,7 @@ class Bundle(implicit compileOptions: CompileOptions) extends Record {
       case (paramName, paramVal: Data) if paramVal.hasBinding => paramName
     }
     if (boundDataParamNames.nonEmpty) {
-      reflectError(s"constructor parameters ($boundDataParamNames) have values that are hardware types, which is likely to cause subtle errors." +
+      reflectError(s"constructor parameters (${boundDataParamNames.sorted.mkString(", ")}) have values that are hardware types, which is likely to cause subtle errors." +
           " Use chisel types instead: use the value before it is turned to a hardware type (with Wire(...), Reg(...), etc) or use chiselTypeOf(...) to extract the chisel type.")
     }
 
diff --git a/chiselFrontend/src/main/scala/chisel3/core/Module.scala b/chiselFrontend/src/main/scala/chisel3/core/Module.scala
index 74479c6b..5ba6dbc8 100644
--- a/chiselFrontend/src/main/scala/chisel3/core/Module.scala
+++ b/chiselFrontend/src/main/scala/chisel3/core/Module.scala
@@ -255,7 +255,14 @@ abstract class BaseModule extends HasId {
     requireIsChiselType(iodef, "io type")
 
     // Clone the IO so we preserve immutability of data types
-    val iodefClone = iodef.cloneTypeFull
+    val iodefClone = try {
+      iodef.cloneTypeFull
+    } catch {
+      // For now this is going to be just a deprecation so we don't suddenly break everyone's code
+      case e: AutoClonetypeException =>
+        Builder.deprecated(e.getMessage, Some(s"${iodef.getClass}"))
+        iodef
+    }
     _bindIoInPlace(iodefClone)
     iodefClone
   }