play.cr

class AError < Exception
  getter foo
  def initialize(@foo : String, message)
    super(message)
  end
end

class BError < Exception
  getter foo
  def initialize(@foo : String, message)
    super(message)
  end
end

class CError < Exception
  getter foo
  def initialize(@foo : String, message)
    super(message)
  end
end

alias MyError = AError | BError | CError

begin
  puts "hi"
rescue ex : MyError
	puts(ex.foo)
end