* @Nullable X>, then users might pass a TypeParameter<Y>, where Y is a subtype of X, while still
   * passing a TypeToken<X>. This would be invalid. Maybe we could accept a TypeParameter<@PolyNull
   * X> if we support such a thing? It would be weird or misleading for users to be able to pass
   * `new TypeParameter<@Nullable T>() {}` and have it act as a plain `TypeParameter<T>`, but

    return new TypeToken<Map<K, V>>() {}.where(new TypeParameter<K>() {}, keyType)
        .where(new TypeParameter<V>() {}, valueType);
  }

  private static <T> TypeToken<T[]> arrayOf(Class<T> componentType) {
    return new TypeToken<T[]>() {}.where(new TypeParameter<T>() {}, componentType);
  }

  public <T> void testNulls() {

    return new TypeToken<Map<K, V>>() {}.where(new TypeParameter<K>() {}, keyType)
        .where(new TypeParameter<V>() {}, valueType);
  }

  private static <T> TypeToken<T[]> arrayOf(Class<T> componentType) {
    return new TypeToken<T[]>() {}.where(new TypeParameter<T>() {}, componentType);
  }

  public <T> void testNulls() {