Stop reporting exceptions in custom transformations as internal errors (#867)

Instead, just forward the exception

1 files changed, 2 insertions, 0 deletions

diff --git a/src/main/scala/firrtl/Driver.scala b/src/main/scala/firrtl/Driver.scala
index 47841cec..c277e120 100644
--- a/src/main/scala/firrtl/Driver.scala
+++ b/src/main/scala/firrtl/Driver.scala
@@ -248,6 +248,8 @@ object Driver {
         case p: PassException    => throw p
         case p: PassExceptions   => throw p
         case p: FIRRTLException  => throw p
+        // Propagate exceptions from custom transforms
+        case CustomTransformException(cause) => throw cause
         // Treat remaining exceptions as internal errors.
         case e: Exception => throwInternalError(exception = Some(e))
       }