Rust-inspired `struct` and `impl` in Ruby for fun

example.rb

require_relative 'kernel'

struct :Point do
  {
    x: 0,
    y: 0,
    z: 0
  }
end
   
impl :Point do
  def to_s
    "(#{x}, #{y}, #{z})"
  end
end
   
point = Point.new
#=> #<struct Point x=0, y=0, z=0>
puts point
#>> (0, 0, 0)

kernel.rb

module Kernel
  def struct(class_name, &block)
    pairs = block.call
    struct = Struct.new(*pairs.keys, keyword_init: true)
    const = Object.const_set(class_name, struct)
    defaults = pairs.compact
    if defaults.any?
      const.class_eval do
        define_method :initialize do
          super(**defaults)
        end
      end
    end
  end

  def impl(class_name, &block)
    const = if Object.const_defined?(class_name)
      Object.const_get(class_name)
    else
      Object.const_set(class_name, Class.new)
    end
    
    const.class_eval(&block)
  end
end