with_exclusive_scope

# File actionpack/lib/action_dispatch/routing/mapper.rb, line 1375
          def with_exclusive_scope
            begin
              old_name_prefix, old_path = @scope[:as], @scope[:path]
              @scope[:as], @scope[:path] = nil, nil

              with_scope_level(:exclusive) do
                yield
              end
            ensure
              @scope[:as], @scope[:path] = old_name_prefix, old_path
            end
          end