Attempt at overriding Struct subclass ::new in Ruby for better kwargs performance

struct2.rb

Struct2 = Class.new(Struct)
Struct2.singleton_class.prepend Module.new {
  def new(...)
    st = super
    st.instance_eval <<~RUBY
      alias __orig_new__ new

      ARG_NOT_GIVEN = Object.new.freeze

      def new(#{st.members[0]} = ARG_NOT_GIVEN, *, **)
        if #{st.members[0]}.equal?(ARG_NOT_GIVEN)
          __kw_new__(**)
        else
          __list_new__(#{st.members[0]}, *)
        end
      end

      def __kw_new__(#{st.members.map { |m| "#{m}:" }.join(',')})
        __orig_new__(#{st.members.map { |m| "#{m}" }.join(',') })
      end

      def __list_new__(#{st.members.map { |m| "#{m}" }.join(',') }, **)
        __orig_new__(#{st.members.map { |m| "#{m}" }.join(',') })
      end
    RUBY
    st
  end

  def method_added(m)
    # revert performance patch that depends on default initialize sig
    alias new __orig_new__ if m == :initialize
    super
  end
}