Infer ZSAError when action is generic?

[ryantbrown]

@IdoPesok Hoping to get some help here. I am having trouble inferring errors as ZSAError when the action is generic:

function useFormAction<
  TAction extends TAnyZodSafeFunctionHandler,
  TSchema extends inferInputSchemaFromHandler<TAction>
  TInput extends inferServerActionInput<TAction>
>({
  action,
  schema,
  ...options
}: ActionOptions<TAction> & {
  action: TAction;
  schema: TSchema;
}) {
  /**
   * Set up the action with field specific error handling.
   */
  const sa = useServerAction(action, {
    ...options,
    onError: ({ err }) => // ^? err is inferServerActionError<TAction> which is not a ZSAError?
  });
}

/**
 * Type for the options of the `useServerAction` hook.
 */
type ActionOptions<
  TAction extends TAnyZodSafeFunctionHandler,
  TPersistError extends boolean = false,
  TPersistData extends boolean = false,
> = Parameters<typeof useServerAction<TAction, TPersistError, TPersistData>>[1];

[ryantbrown]

{
...options,
onError: ({ err }) => {
    // TypeScript has no idea what err is at all
    // The left-hand side of an 'instanceof' expression must be of type 'any', an object type or a type parameter.
    if (err instanceof ZSAError) {}
  }
}