Spinal can’t clone class

Introduction

This error happens when SpinalHDL wants to create a new datatype instance via the cloneOf function but isn’t able to do it. The reason for this is nearly always because it can’t retrieve the construction parameters of a Bundle.

Example

The following code:

// cloneOf(this) isn't able to retrieve the width value that was used to construct itself
class RGB(width : Int) extends Bundle {
  val r, g, b = UInt(width bits)
}

class TopLevel extends Component {
  val tmp = Stream(new RGB(8)) // Stream requires the capability to cloneOf(new RGB(8))
}

will throw:

*** Spinal can't clone class spinal.tester.PlayDevMessages$RGB datatype
*** You have two way to solve that :
*** In place to declare a "class Bundle(args){}", create a "case class Bundle(args){}"
*** Or override by your self the bundle clone function
  ***
  Source file location of the RGB class definition via the stack trace
  ***

A fix could be:

case class RGB(width : Int) extends Bundle {
  val r, g, b = UInt(width bits)
}

class TopLevel extends Component {
  val tmp = Stream(RGB(8))
}