* `new TypeParameter<@Nullable T>() {}` and have it act as a plain `TypeParameter<T>`, but
   * hopefully no one would do that, anyway. See also the comment on TypeParameter itself.
   *
   * TODO(cpovirk): Elaborate on this / merge with other comment?
   */
  public final <X> TypeToken<T> where(TypeParameter<X> typeParam, TypeToken<X> typeArg) {
    TypeResolver resolver =
        new TypeResolver()
            .where(