elixir_type_test.ex

defmodule Nothing do
  defstruct([])

  @type t :: %__MODULE__{}
end

defmodule Name do
  defstruct first: "", last: ""

  @type t :: %__MODULE__{first: String.t, last: String.t}
end

defmodule Character do
  @type t :: %__MODULE__{
    name: Name.t | Nothing.t
  }

  defstruct name: %Nothing{}

  # dialyzer return an error for this function
  @spec return_test :: Name.t | Nothing.t
  def return_test, do: "Dan"

  # dialyzer does not give an error for this function event though
  # name does is a string instead of Name.t | Nothing.t
  @spec return_dan :: __MODULE__.t
  def return_dan, do: %Character{name: "Dan"}
end