public static Object[] despreadList(Object[] args, Object[] spreads, int[] positions) {
    return ScriptBytecodeAdapter.despreadList(args, spreads, positions);
  }
Need to be careful because this converts null to an empty array.
For single arguments, new Object[] {arg} should therefore be used.
spock-core/src/main/java/org/spockframework/runtime/GroovyRuntimeUtil.java