private void collectParameterGenerators()
    {
        Generator[] generators = getParameterAnnotations(Generator.class);
        for (int i = 0; i < generators.length; ++i) {
            if (generators[i] != null) {
                Class<? extends Gen<?>> genClass = generators[i].generator();
                fromPositionGenerators.put(i, genClass);
            }
        }
    }