A simple result monad implemented with type safety using sorbet

result_monad.rb

# frozen_string_literal: true
# typed: true

require 'sorbet-runtime'

# Result...
module Result
  extend T::Sig

  # Ok...
  class Ok < T::Struct
    extend T::Generic
    OkVal = type_member

    prop :_tag, String, default: 'Ok'
    prop :value, OkVal
  end

  # Err...
  class Err < T::Struct
    extend T::Generic
    ErrVal = type_member

    prop :_tag, String, default: 'Err'
    prop :value, ErrVal
  end
end

# Test...
module Test
  extend T::Sig

  sig { params(blau: String).returns(T.any(Result::Ok[String], Result::Err[Integer])) }
  def self.do_something(blau)
    return Result::Err.new(value: 'deu bosta') if blau == 'error'

    Result::Ok.new(value: blau)
  end
end

my_stuff = Test.do_something('another')

puts my_stuff

case my_stuff
in Result::Ok
  puts "OK Value is: #{my_stuff.value}"
in Result::Err
  puts "Error Value is: #{my_stuff.value}"
end