foreign_key

# File activerecord/lib/active_record/reflection.rb, line 558
      def foreign_key(infer_from_inverse_of: true)
        @foreign_key ||= if options[:foreign_key]
          if options[:foreign_key].is_a?(Array)
            options[:foreign_key].map { |fk| -fk.to_s.freeze }.freeze
          else
            options[:foreign_key].to_s.freeze
          end
        elsif options[:query_constraints]
          options[:query_constraints].map { |fk| -fk.to_s.freeze }.freeze
        else
          derived_fk = derive_foreign_key(infer_from_inverse_of: infer_from_inverse_of)

          if active_record.has_query_constraints?
            derived_fk = derive_fk_query_constraints(derived_fk)
          end

          if derived_fk.is_a?(Array)
            derived_fk.map! { |fk| -fk.freeze }
            derived_fk.freeze
          else
            -derived_fk.freeze
          end
        end
      end