gistfile1.txt

class Class1
  def dupa
    puts "Dupa from Class1"
  end
end

class Class2
  def dupa
    puts "Dupa from Class2"
  end
end

alias Dupa = (Class1.class | Class2.class)

class Buzz
  def initialize
    # @arr = [] of (Class1.class | Class2.class)
    @arr = [] of Dupa
  end

  def add(class_name : Class)
    @arr << class_name
  end

  def run_dupas
    @arr.each do |class_name|
      class_name.new.dupa
    end
  end

  def dump
    pp @arr
  end
end

buzz = Buzz.new
buzz.add(Class1)
buzz.add(Class2)
buzz.dump
buzz.run_dupas