new

# File actionpack/lib/action_dispatch/routing/mapper.rb, line 21
        def initialize(app, constraints, dispatcher_p)
          # Unwrap Constraints objects.  I don't actually think it's possible
          # to pass a Constraints object to this constructor, but there were
          # multiple places that kept testing children of this object.  I
          # *think* they were just being defensive, but I have no idea.
          if app.is_a?(self.class)
            constraints += app.constraints
            app = app.app
          end

          @dispatcher = dispatcher_p

          @app, @constraints, = app, constraints
        end