assertThrows(
        NullPointerException.class, () -> fluent(1, 2, 3).uniqueIndex(Functions.constant(null)));
  }

  public void testUniqueIndex_nullValue() {
    assertThrows(
        NullPointerException.class,
        () -> {
          ImmutableMap<Object, Integer> unused =
              fluent(1, null, 2)
                  .uniqueIndex(
                      new Function<Integer, Object>() {

	// In some db (e.g. MySQL), Unique and UniqueIndex are indistinguishable.
	// When a column has a (not Mul) UniqueIndex, Migrator always reports its gorm.ColumnType is Unique.
	// It causes field unnecessarily migration.
	// Therefore, we need to record the UniqueIndex on this column (exclude Mul UniqueIndex) for MigrateColumnUnique.
	UniqueIndex string
}

func (field *Field) BindName() string {

	tidbSkip(t, "not support the foreign key feature")

	type Profile struct {
		ID       uint
		Name     string
		MemberID uint
	}

	type Member struct {
		ID      uint
		Refer   uint `gorm:"uniqueIndex"`
		Name    string
		Profile Profile `gorm:"Constraint:OnUpdate:CASCADE,OnDelete:CASCADE;FOREIGNKEY:MemberID;References:Refer"`
	}

	DB.Migrator().DropTable(&Profile{}, &Member{})

	unique, ok := columnType.Unique()
	if !ok || field.PrimaryKey {
		return nil // skip primary key
	}
	// By default, ColumnType's Unique is not affected by UniqueIndex, so we don't care about UniqueIndex.
	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
		// We're currently only receiving boolean values on `Unique` tag,
		// so the UniqueConstraint name is fixed

   * @since 14.0
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final <K> ImmutableMap<K, @NonNull E> uniqueIndex(Function<? super E, K> keyFunction) {
    return Maps.uniqueIndex((Iterable<@NonNull E>) getDelegate(), keyFunction);
  }

  /**
   * Returns an array containing all of the elements from this fluent iterable in iteration order.
   *

   * @since 14.0
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final <K> ImmutableMap<K, @NonNull E> uniqueIndex(Function<? super E, K> keyFunction) {
    return Maps.uniqueIndex((Iterable<@NonNull E>) getDelegate(), keyFunction);
  }

  /**
   * Returns an array containing all of the elements from this fluent iterable in iteration order.
   *