whenOrNull<TResult extends Object?>  method 
- @optionalTypeArgs
- TResult? primitiveArray(- LexPrimitiveArray data
 
- TResult? primitive(- LexPrimitive data
 
A variant of when that fallback to returning null
It is equivalent to doing:
switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case _:
    return null;
}
Implementation
@optionalTypeArgs TResult? whenOrNull<TResult extends Object?>({TResult? Function( LexPrimitiveArray data)?  primitiveArray,TResult? Function( LexPrimitive data)?  primitive,}) {final _that = this;
switch (_that) {
case ULexXrpcParametersPropertyPrimitiveArray() when primitiveArray != null:
return primitiveArray(_that.data);case ULexXrpcParametersPropertyPrimitive() when primitive != null:
return primitive(_that.data);case _:
  return null;
}
}