private final ImmutableList<Type> lowerBounds;
    private final ImmutableList<Type> upperBounds;

    WildcardTypeImpl(Type[] lowerBounds, Type[] upperBounds) {
      disallowPrimitiveType(lowerBounds, "lower bound for wildcard");
      disallowPrimitiveType(upperBounds, "upper bound for wildcard");
      this.lowerBounds = JavaVersion.CURRENT.usedInGenericType(lowerBounds);