class RuboCop::Cop::Rails::UniqueValidationWithoutIndex

def with_index?(klass, table, names)
  # Compatibility for Rails 4.2.
  add_indices = schema.add_indices_by(table_name: table_name(klass))
  (table.indices + add_indices).any? do |index|
    index.unique && (index.columns.to_set == names || include_column_names_in_expression_index?(index, names))
  end
end